PEAK TANK-Compartments at the extreme fore and aft ends of the ship for any use either as void spaces or as trimming tanks. When used for the latter purpose water is introduced to change the trim of the vessel.

PERPENDICULAR-Vertical lines extending through the outlines of the hull ends and the designer's waterline.

PITCHING-The alternate rising and falling motion of a vessel's bow in a nearly vertical plane as she meets the crests and troughs of the waves.

PLAT-A map or plan view of a lot showing principal features, boundaries, and location of structures,

PLATFORM-A partial deck.

PLATING, SHELL-The plating forming the outer skin of a vessel. In addition to constituting a watertight envelope to the hull, it contributes largely to the strength of the vessel.

PLIMSOLL MARK-A mark painted on the sides of a vessel designating the depth to which the vessel may, under the maritime laws, be loaded in different bodies of water during various seasons of the year.

POOP-The structure or raised deck after end of a vessel.

POUNDS PER SQUARE INCH (psi)-Unit of pressure.

POUNDS PER SQUARE INCH GAUGE (psig)-Unit of pressure.

PRESSURE-Pressure is force per unit of area, usually expressed as psi.

PROTECTED COMPARTMENT-A compartment with a fixed (total flooding) carbon dioxide system installed.

PYROTECHNICS-(1) Ammunition containing chemicals that produce smoke or a brilliant light in burning; used for signaling or for illumination. (2) Flares, rockets, powder, etc., used for giving signals or for illumination, more generally used as distress signals.

RADIATION-Transfer of heat in the form of waves similar to light and radio waves, without physical contact between the emitting and the receiving regions.

REFERENCE PLANE-On a drawing, the normal plane from which all information is referenced.

RISER-(1) An opening made from the mold cavity to the top of the mold in which the metal will rise during the pouring operation and which may later act as a feeder for the prevention of porosity in the casting due to shrinkage. (2) A reservoir designed to supply molten metal to compensate for shrinkage of a casting during solidification. (3) A pipe leading from the firemain to fireplugs on upper deck levels. (4) A vertical pipe leading off a large one; for example, firemain riser. (5) A vertical casualty control cable leading from deck to another. (6) The upright board of a stair. A pipe extending vertically and having side branches. (7) A distribution pipe extending vertically.

RIVET-A metal pin used for connecting two or more pieces of material by inserting it into holes punched or drilled in the pieces and upsetting one or both ends. The end that bears a finished shape is called the head and the end upon which some operation is performed after its insertion is called the point. Small rivets are "driven cold," i.e., without heating, and large ones are heated so that points may be formed by hammering.

SCUTTLE-(1) A small opening, usually circular in shape and generally fitted in decks to provide access. Often termed escape scuttles, and when fitted with means whereby the covers can be removed quickly to permit exit are called quick acting scuttles. (2) Round, watertight opening in a hatch. (3) The act of deliberately sinking a vessel.

SECOND DECK-First complete deck below the main deck.

SECTION LINES-Thin, diagonal lines used to indicate the surface of an imaginary cut in an object.

SELECTOR SWITCH-Usually a rotary-type switch with more than two line connections. The selector switch permits the connection of a permanently connected handset to any other circuit selected-that is, wired in, by means of a jack outlet. In some stations, where only two circuits are involved, a double-throw toggIe switch is sufficient.

SHOLE-A small piece of timber or plank placed under the heel of a shore.

SHORE-(1) The land in general, but usually refers to that part adjacent to the water; (2) a timber used in damage control to brace bulkheads and decks.

SOFT PATCH-A temporary plate put on over a break or hole and secured with tap bolts. It is made watertight with a gasket such as canvas saturated in red lead.

STABILITY, RANGE OF-The number of degrees through which a vessel rolls or lists before losing stability.

STERN-The after end of a vessel; the farthest distant part from the bow.

STIFFENER-An angle bar, T-bar, channel, etc., used to stiffen plating of a bulkhead, etc.

STRUCTURAL BULKHEAD-Transverse strength bulkhead that forms a watertight boundary.

STUFFING TUBE-A packed tube that makes a watertight fitting for a cable or small pipe passing through a bulkhead.

TOGGLE PIN-A pin having a shoulder and an eye worked on one end, called the head, and whose other end, called the point, has its extremity hinged in an unbalanced manner so that after being placed through a hole it forms a T-shaped locking device to keep the pin from working out or being withdrawn without first bringing the hinged portion into line with the shaft of the pin.

TRANSVERSE-At right angles to the ship's fore-and-aft centerline.

TRIM-The arithmetical sum of the drafts forward and aft above and below the mean waterline. The angle of trim is the angle between the plane of flotation and the mean waterline plane. A vessel "rims by the head" or "trims by the stern" when the vesseI inclines forward or aft so that her plane of flotation is not coincident with her mean waterline plane. See DRAG.

WATERLINE-(1) A term used to describe a line drawn parallel to the molded baseline and at a certain height above it, as the 10-foot waterline. It represents a plane parallel to the surface of the water when the vessel is floating on an even keel, i.e., without trim. In the body plane and the sheer plan it is a straight line, but in the plan view of the lines it shows the contour of the hull line at the given distance above the base line. Used also to describe the line of intersection of the surface of the water with the hull of the ship at any draft and any condition of trim. (2) The outline of a horizontal longitudinal section of a ship's hull.

WATERTIGHT COMPARTMENT-A space or compartment within a ship having its top, bottom, and sides constructed in such a manner as to prevent the leakage of water into or from the space unless the compartment is ruptured.

WATERTIGHT INTEGRITY-The degree or quality of watertightness.

WEATHER DECK-A term applied to the upper, awning, shade, or shelter deck, or to the uppermost continuous deck, exclusive of forecastle, bridge, or poop, that is exposed to the weather.

WEDGES-Wood or metal pieces shaped in the form of a sharp V, used for driving up or for separating work. They are used in launching to raise the vessel from the keel blocks and thus transfer the load to the cradle and the sliding ways.

WEIGHT-The force of gravity exerted on an object.

WHEATSTONE BRIDGE-A device for the measurement of electrical resistance.

WINDWARD-Toward the direction from which the wind is blowing.

WIREWAYS-Passageways between decks and on the overheads of compartments that contain electric cables.

WYE GATE-A fitting with two separately controlled hose fittings, designed to connect to an outlet.

ZONE NUMBERS-Numbers and letters on the border of a drawing to provide reference points to aid in indicating or locating specific points on the drawing.