Return to the Naval Historical Center Home Page

Banner image, Nomenclature of Naval Vessels

Navy seal

Revised February 1942


S T U V W X  Y  Z

First Printing June 1942

Prepared by





The requirements of navy yards and stations, private shipbuilding plants and vocational defense training schools for NOMENCLATURE OF NAVAL VESSELS, in connection with their training programs, have exhausted the first edition. However, in reprinting this pamphlet it has been revised to make it more complete, and to include the charts of ships' section which were developed at the Navy Yard, Philadelphia, Pennsylvania.

Charles Piozet,
Director of Personnel.



"Nomenclature of Naval Vessels" has been prepared primarily for use in the apprentice schools at the various navy yards and stations. It is believed, however, that it will be found useful for reference purposes by engineers, draftsmen, inspectors, and others interested in the construction of naval vessels.

The materials developed in the courses of instruction for "in-service" training at the Navy Yards, Mare Island, Philadelphia, and Boston, have been used in the preparation of this book. The Design Division of the Bureau of Ships assisted in compiling and revising the material.

Charles Piozet,
Director of Personnel.



In its construction, a ship or vessel, like a building, is started on its foundation and carried through to completion by the fitting and securing of its many parts together to form a designed shape. However, the nomenclature of the several members of which the ship is composed and the parts and spaces provided in its erection differs from that used for buildings.

The foundation of a ship is called the KEEL and extends FORE and AFT from BOW to STERN, which, when speaking of a building in a similar way, would be from front to back. The STEM is located at the very forward end of the keel and the STERN POST to which the RUDDER is attached is at the after end. The keel is the "backbone" of the ship, and extending outward from it to form the "ribs" or framing of the ship are the FRAMES, to which steel PLATES are welded or riveted to form the "skin" or SHELL of the ship.

The ship is divided into it many spaces by "walls" called BULKHEADS, and these spaces or rooms are called COMPARTMENTS or TANKS as the case may be. Corresponding to the floors of a building of several stories are the DECKS and PLATFORMS which are made of steel plates laid across steel beams called DECK BEAMS. The "windows" of a ship are called PORTHOLES, and entrance into compartments or tanks is gained through DOORS, HATCHWAYS, SCUTTLES, or MANHOLES. The "chimneys" are called STACKS or FUNNELS. The ship is driven through the water by the PROPELLER, sometimes called the WHEEL, and it is steered by the RUDDER.

Looking from the stern in a direction toward the bow, the right-hand side of the ship is called STARBOARD, the left-hand side, PORT. When a ship is being constructed, the frames are shown on blueprints and are numbered from the forward toward the stern commencing with the first frame at the bow of the ship. The zero point is taken at the FORWARD PERPENDICULAR, which is a design point on the stem of the ship, the first frame aft of this point being called FRAME #1, the second, #2, and continuing consecutively to the AFTER PERPENDICULAR which is a design point located at the after end of the ship. Usually frames on a ship are


evenly spaced; however, in some sections, as for example, the very bow of the ship, the frames are close together due to strength requirements. The various units placed aboard ship are located fore and aft, according to a position, relative to a certain distance from the closest frame; up or down relative to a certain distance above or below a particular deck or the base line; and port or starboard relative to a certain distance from the CENTER LINE of the ship.

The following expression is given as an example of ship terms, and shows how a workman would locate himself aboard ship to do a job assigned to him. He steps ABOARD ship from a "walk" called a GANGWAY, walks across the deck to either the PORT or STARBOARD side (as the case may be), goes (upstairs) ALOFT or TOPSIDE by means of a "stairs" called a LADDER to the DECK above (do not say upstairs or downstairs); or after crossing the DECK, he goes through a HATCHWAY below on the LADDER to the second deck, walks forward along a "hall" called a passageway, goes through another HATCHWAY and down the ladder to the first PLATFORM, walks along another passageway and removes a MANHOLE COVER to gain entrance to the COMPARTMENT below, which happens to be located between frames #26 and #35.

A naval vessel, when constructed with both an inner and an outer bottom, has a DOUBLE BOTTOM, the spaces between the inner and outer bottoms being called DOUBLE BOTTOM TANKS. This construction provides protection against flooding of compartments and possible sinking of the ship should a hole be torn in the outer bottom. BULKHEADS between compartments and other sections of the ship are made oiltight or watertight to prevent leakage should adjacent compartments be filled with oil or water, respectively. The HULL or SHELL must also be made watertight.

The shell plates are laid end to end in rows called STRAKES from stem to stern, some of the strakes being given special names; as, for example, the bottom strake port and starboard next to the keel is called the GARBOARD STRAKE. Plates are usually spoken of by weights instead of thicknesses, said weight being the weight for a square foot of plate surface of a given thickness. A 5-pound plate is a plate 1/8 inch thick, each square foot weighing 5 pounds, and using this as a factor, a 71/2-pound plate would be 3/16 inch thick, a 10-pound plate, 1/4 inch thick; a 20-pound plate, 1/2 thick, etc.


Various structural shapes are used for framing and strength members in ships. Some of the shapes (shown in cross section) are as follow:



There are two types of decks--complete decks and partial decks. A complete deck is a deck running the full length of the ship and a partial deck is a deck running only part of the length of the ship. Decks are named according to their location above or below the main deck, which is the highest deck extending from stem to stern.

A partial deck above the main deck at the bow is called the "forecastle deck"; at the stern, "poop deck"; admidships, "upper deck." The name "upper deck," instead of "forecastle deck" or "poop deck," is applied to a partial deck extending from amidships to either bow or stern. A partial deck above the main, upper, forecastle, or poop deck and not extending to the side of the ship is called the "superstructure deck."

A complete deck below the main deck is called the "second deck." Where there are two or more complete decks below the main deck, they are called the "second deck," "third deck," "fourth deck," etc. A partial deck above the lowest complete deck and below the main deck is called the "half deck." A partial deck below the lowest complete deck is called a "platform." Where there are two or more partial decks below the lowest complete deck, the one immediately below the lowest complete deck is called the "first platform," the next is called "second platform," and so on.

Decks which for protective purposes are fitted with plating of extra strength and thickness are further defined, for technical purposes, as "protective" and "splinter," in addition to their regular names. Where there is only one such deck, it is defined as "protective" and where there are two, the lower one is defined as "splinter" in addition to the regular names.

Watertight compartments are specified by letters and numbers. Compartments in each division are numbered beginning at the forward end of each division. The ship is considered as divided into three principle divisions, lettered, A, B, C, from forward aft.

Division A.-- This comprises all of the space between the stem and the forward transverse bulkhead of the forward machinery compartment.

Division B.-- This comprises all of the space between the forward transverse bulkhead of the forward machinery compartment and the after transverse bulkhead of the after machinery compartment.

Division C.-- This comprises all of the space aft of the after transverse bulkhead of the after machinery compartment.

The term "machinery compartment" is construed as meaning firerooms, boiler rooms, engine rooms, main motor rooms, main machinery


spaces, and compartments in which auxiliaries of the main propelling machinery are located. Where the number of the compartments in the 1 to 100 series exceeds 100 in any principal division, the matter is referred to the Bureau of Ships. These divisions are considered as extending from the keel to the highest deck in the line of the bulkheads, or the bulkheads prolonged. In case the bulkheads do not extend to the highest deck, any space between decks that extends through two of the principal divisions is numbered as if it were situated entirely in the forward division of the two in which it is placed, and has this number only. Main compartments with permanent openings to the top side, such as boiler rooms, are considered as completely bounded by tight structure for numbering purposes.

All numbers in each division begin at the forward end of that division. Compartments on the starboard side of the ship have odd numbers; those on the port side, even numbers. All compartments and spaces that are completely bounded by watertight, oiltight, airtight, or fumetight structure are numbered. Where a watertight compartment located below the weather deck is divided into two or more airtight or fumetight spaces by airtight or fumetight bulkheads, the appropriate number is assigned the watertight compartment and each airtight or fumetight subdivision within the compartment is designated by the addition of a suffix to this number. Thus, if watertight compartment A-312L contains a fumetight or airtight longitudinal bulkhead, the space to starboard of this bulkhead is designated as A-312-1L and the space to port as A-312-2L.

Oiltight and watertight compartments in each division on the main deck are numbered from 101 to 199, and those on each successive deck or platform below the main deck are number in the next higher hundred series; namely, those on the second deck are numbered from 201 to 299; on the third deck, from 301 to 399, etc. Watertight compartments on the next deck or platform above the main deck are numbered 0101 to 0199, and those on each successive deck or platform above the main deck are numbered in the next higher hundred series, prefixed with a zero. For example, a ship that has a superstructure, forecastle, main, second and third deck, and a first and second platform, the oiltight and watertight compartments are numbered as follows:

On superstructure deck 0201 to 0299
On forecastle deck 0101 to 0199
On main deck 101 to 199
On second deck 201 to 299
On third deck 301 to 399
On first platform 401 to 499
On second platform 501 to 599
In hold, if there are no more platforms 601 to 699


Upper inner bottom compartments are numbered from 801 to 899 and lower inner bottom compartments are numbered 901 to 999. It will be noted that the prefix zero of a compartment number indicates that the compartment is above the main deck. If there is not a third deck, the compartments on the first and second platforms and in the hold are numbered 301 to 399, 401 to 499, and 501 to 599, respectively. If there is a fourth deck, the compartments on the fourth deck and first and second platforms and hold are 401 to 499, 501 to 599, 601 to 699, and 701 to 799, respectively.

On modern destroyers the compartment numbers in each division are as follows:

On main deck 101 to 199
On first platform 201 to 299
On second platform 301 to 399
In hold 401 to 499

Compartments in each division with no decks, extending from inner bottom or outside plating through two or more deck spaces, such as those in protective layers, engine rooms, boiler rooms, deep peak tanks, fuel-oil tanks on certain battleships, cargo holds, etc., are numbered from 1 up to 100. Boiler and engine rooms are given the lowest numbers, B-1, B-2, B-3, etc. Where there is a half deck owing to the sheer or other cause, or where there is a flat between regular decks, such as cofferdam flat over oil tank, no change in the hundred series in made on account thereof. The above scheme of numbering is intended to give an indication of the vertical location of the compartment which, in connection with the divisional fore and aft location, will give a very fair idea of the position of the compartment.

The number of a compartment is always prefixed with the letter indicating the general division of the ship in which it is placed and separated from the number by a hyphen, as A-21, B-3, etc.

To define further the contents or main use of a compartment, the compartment number is followed by a designating letter, as follows:

A for storerooms, including:
Band room.
Refrigerator compartments.
Storerooms proper.
Tool and supply rooms.
Unassigned compartments usable as storerooms.
B for battery compartments, including:
Secondary battery compartments.
Torpedo rooms.
All compartments within turrets, including turret-handling rooms.


C for ship control and fire control, including:
Coding room.
Interior communication.
Main communication station.
Plotting room.
Radio rooms.
Switchboard room (secondary battery).
Torpedo tracking room.
E for machinery compartments, including:
Blower room.
Boiler room.
Distribution room.
Evaporator room.
General workshop.
Gyro stabilizer room.
Ice-machine room.
Main engine room.
Main motor room.
Main operating room.
Pump room.
Searchlight rheostat room.
Shaft alley.
Steering gear room.
Storage battery room.
Thrust block room.
Windlass room and chain locker.
NOTE.--The E may be omitted from the main propelling machinery compartments, comprising main engine rooms, boiler rooms, and main motor rooms.
F for fuel compartments, including:
Fuel compartments.
Diesel oil compartments.
Relay tank rooms.
LUB for lubricating oil storage tanks.
GAS for gasoline compartments, including:
Gasoline storage tanks. Gasoline tank compartments.
L for living compartments, including:
Crew's spaces.
Officers' quarters.
Water closet and wash rooms.
M for ammunition spaces, including:
Bomb magazines.
Catapult charge magazines.
Fixed ammunition magazines.
Handling rooms except turret.
Mine charge magazines.
Powder magazines.
Shell rooms.
Small-arms magazines.
Torpedo war head magazines.
V for void compartments, including:
Cofferdam compartments.
Void double-bottom compartments.
Void wing compartments.
W for water compartments, including:
Drainage tanks.
Fresh-water compartments.
Peak tanks.
Reserve feed compartments.


A double-bottom compartment used for feed water is designated B-910 W, for oil B-909 F, if void A-902 V. When a space is devoted to several main purposes, two or more designating letters are used. Thus a living compartment containing a secondary battery guns is designated B-115 B L.


Fireroom.-- A compartment containing boilers and the station for "firing" or operating same.

Boiler room.-- A compartment containing boilers but not containing station for "firing" or operating the boilers.

Boiler operating station.-- A station from which a boiler or boilers are operated.

Boiler central control station.-- A station for directing control of all boilers at boiler operating stations.

Boiler emergency station.-- A station for a chief water tender from which he may proceed with minimum delay to any fireroom, boiler operating station, or boiler room from which trouble has been reported.

Engine room.-- A compartment in which the main propelling unit or units are installed.

Engine operating station.-- A location or compartment from which a main propelling unit or units are operated.

Machinery spaces.-- A collective term designating all the major compartments in which machinery under the cognizance of the Bureau of Ships is located.


The number of compartments is shown by means of label plates and tags of two types--engraved and embossed. Doors, hatches, and manholes are also numbered by means of label plates and tags. The inscription on door, hatch, or manhole plates is combined with that of the compartment or several compartments to which they provide access. Label plates are placed in a conspicuous location where they may be readily seen. Specifications for labelling are described in the pamphlet "General Specifications--Appendix 10" issued by the Bureau of Ships.

The following is an example of an inscription taken from the label plate on a door:

C.P.O. Stores

The first line of the inscription is the number of the door, the second, the designation of the compartment, and the third, the compartment number to which the door gives access.


From the above it will be noted that the door, hatch, or manhole number consists of two or three parts, separated by hyphens. The first part corresponds to the deck number; the next part, the frame number just forward of the hinge of the door; and the last part, the number of the door, if there is more than one door on the same frame on the deck designated by the first part; if not, the third part may be omitted. For the first part of their numbers, hatches and manholes take the number of the deck through which they are cut. Odd numbers are used in the third part for doors located on the starboard side and even numbers on the port side. For example:

Door 3-24-1 is on the third deck, frame 24, or between frames 24 and 25, starboard side.

Door 3-24-2 is on the third deck, frame 24, or between frames 24 and 25, port side.

Hatch 3-24-2 is on the third deck at or immediately aft of frame 24 on the port side.

In the principle living compartments and elsewhere throughout the length of a ship as may be necessary to locate readily a particular place, every fifth frame is numbered in accordance with "General Specifications--Appendix 10." The numbers may be seen on the seen on the beams in a conspicuous place along passageways and other routes of travel and are located as near the bottom edge of a beam as practicable.

Abbreviations allowable when inscription are long are as follows:

Amm. for ammunition. Med. for medical.
A.T. for airtight. M.T. for flametight.
Aux. for auxiliary. Nav. for navigation.
BH. for bulkhead. N.T. for nontight.
Circ. for circulating. Offs. for officers.
Compt. for compartment. Ord. for ordnance.
Const. for construction. O.T. for oiltight.
C.P.O. for chief petty officers. R.S. Mag. for ready-service magazine.
Cu. ft. for cubic feet. Sal. Pwdr. for saluting powder.
Dis. for discharge. S.D. for supply department.
Elec. for electric. Sergt. for sergeant.
Equip. for equipment. Stbd. for starboard.
Evap. for evaporator. Suc. for suction.
For'd. for forward. T. for tons.
F.O. for fuel oil. Torp. for torpedo.
Fr. for frame. Trans. for transverse.
F.T. for fumetight. Vent. for ventilation.
Ft. for feet or foot. V.T. for voice tube.
F.W. for fresh water. W. for weathertight.
Gals. for gallons. W.C. for water closet.
In. for inch. W.L. for waterline.
J.O. for junior officers. W.O. for warrant officers.
L.O. for lubricating oil. W.R. for wardroom.
Mag. for magazines. W.T. for watertight.
M.H. for manhole.    


A more definite idea of the various parts of the hull of a ship may be obtained by closely examining a ship model in the Apprentice School or Drafting Room, and the plates at the back of this book.


25 August 2003