Anti-cavitation plate On a narrowboat, a plate fitted flush to the uxter plate to cover the weedhatch opening.


Backstay Part of the standing rigging that supports the mast; it reaches from the stern of the vessel to the mast head.

Baggywrinkle A soft covering for stays and other standing rigging that prevents sail chafing.

Batten A stiff strip used to support the roach of a sail.

Beam The width of a vessel at the widest point.

Bermudan rig A triangular mainsail, without any upper spar, which is hoisted up the mast by a single halyard attached to the head of the sail.

Berth A bed or sleeping accommodation on a boat or ship.

Bilge The compartment at the bottom of the hull of a ship or boat where water collects and must be pumped out of the vessel.

Bilge keel A keel on fastened to the hull off the centre line, often close to the turn of the bilge. They allow a vessel stand upright on two bilge keels, on a drying mooring.

Bitts A post or pair mounted on the ship's bow, for fastening ropes or cables.

Block A pulley or set of pulleys.

Bobstay A stay which holds the bowsprit downwards, counteracting the effect of the forestay.

Boom A spar attached to the foot of a fore-and-aft sail.

Boom vang A sail control that lets one apply downward tension on a boom, countering the upward tension provided by the sail.

Bottlescrew A device for adjusting tension in stays, shrouds.

Bowsprit A spar projecting forward of the bow.

Bow thruster A small propeller or water-jet at the bow, used to turn a vessel at slow speed. Often mounted in a tunnel running through the bow.

Bridge A structure above the weather deck, extending the full width of the vessel.

Brightwork Exposed varnished wood or polished metal on a boat.

Bulkhead An upright wall within the hull of a ship. Particularly a structural wall which is often watertight.

Bulwark The extension of the vessel's hull wall above the level of the weather deck.

Bumpkin A spar, similar to a bowsprit, but which projects from the stern.


Cant On a narrowboat, a raised outer section of a deck normally to the fore and counter decks.

Carvel A constructing wooden hulls by fixing planks to a frame so that the planks butt up against each other to form a smooth hull, where the plank seams cannot easily be seen.

Catamaran A vessel with two hulls.

Chine An angle in the hull. There may be several chines, depending upon the hull design. A narrowboat often has a single chine where the hull wall and the bottom plate meet.

Clench A method of fastening in wooden boats using copper boat nails and a rove (similar to a washer). The nail is then burred or riveted over to complete the fastening.

Clew On a triangular sail, the bottom aft corner, to which the sheets bent on a loose-footed sail.

Clinker A method of constructing hulls that involves overlapping planks.

Coaming The raised edge of a hatch, cockpit or skylight.

Cockpit The area towards the stern of a small decked vessel that houses the rudder controls and seating.

Companionway A stairway from one deck to another.

Counter The part of the stern above the waterline that extends beyond the rudder stock. On a narrowboat the counter stern is trimmed to float at the waterline.

Counter plate On a narrowboat, the stern section of the hull side plating above the waterline that wraps around the stern and corresponds to the counter swim.

Crance or Cranze A fitting, mounted at the end of a bowsprit to which forestay and bobstay attach.

Cratch On a narrowboat, a canvas covering over the forward well deck.

Cratch board A triangular board or frame supporting the forward end of the cratch covers.

Cuddy A small cabin in a boat.


Deckhead The under-side of the deck above sometimes covered by the head lining.

Displacement The weight of water displaced by the immersed volume of a vessel's hull and equal to the total weight of the vessel.

Displacement hull A hull design that travels through the water, rather than planing over it.

Dolly On a narrowboat, a round bollard used for mooring.

Draft The depth of water a vessel draws, from the waterline to the lowest part of the keel.


Fair A smooth curve, usually referring to a line of the hull which has no deviations.

Fairlead A ring, hook or other device to keep a line or chain running in the correct direction to prevent it fouling or chafing.

Flare The widening of the topsides outward from the waterline the gunwale.

Foot The lower edge of a sail.

Foot or Footing On a narrowboat, the lower section of the hull side.

Forefoot The lower part of the stem of a vessel.

Forestay Part of the standing rigging that reaches from the bow of the vessel to the mast heads.

Frame A transverse structural member which gives the hull strength and shape. Freeboard The height of a vessel's hull above the waterline.

Futtock One of several sawn pieces that make up a frame.


Gammon iron The fitting which clamps the bowsprit to the stem.

Garboard The plank closest to the keel.

Gennaker A large, lightweight sail used for sailing a fore-and-aft rig down or across the wind, intermediate between a genoa and a spinnaker.

Genoa A large jib, strongly overlapping the mainmast.

Gooseneck The fitting that attaches the boom to the mast.

GRP Glass reinforced plastic, a type of fibre reinforced plastic. Polyester resin is the most common plastic used in yachts and small craft.

Gudgeon A metal fitting with an eye that is bolted to the transom or sternpost to support the rudder. The pintle passes through the eye.

Gunwale Upper edge of the hull.


Hawsehole The hole in the vessel's deck through which the anchor chain passes.

Hawsepipe The pipe in a vessel's bow through which the anchor chain passes.

Head The upper corner of a triangular sail

Heads A name retained from the past for modern a modern lavatory and flushing mechanism.

Headboard A board used to stiffen the head of a sail; the headboard reinforces the holes in the sail where the main halyard is fastened.

Hog A fore-and-aft structural member of the vessel's backbone. It lies over the keel to provide a fixing for the garboard planks.

Holiday A gap in the coverage of paint or other coating.

Horn timber A fore-and-aft structural member of the hull sloping up and backwards from the keel to support the counter.

Horse On a yacht, the mainsheet is invariably attached to a horse rather than the deck.

Hull speed The maximum efficient speed of a displacement hull.


Jackstays Usually steel wire attached to the decks that provide a secure point for crew to clip their safety lines.

Jib A triangular staysail set forward of the mast.


Kedge A relatively light anchor known used as a secondary anchor.

Kelson The timber immediately above the keel of a wooden ship.

King plank The centreline plank of a laid deck

Knee Internal support connect two parts roughly at right angles, e.g. deck beams to frames. When vertical they are known as hanging knees.


Lazarette A stowage locker at the aft end of a boat.

Lazyjacks A network of cordage rigged that forms a cradle to a sail onto the boom when it is lowered.

Leech The aft edge of a fore-and-aft sail; the leeward edge of a spinnaker

LOA Length overall; the length of a vessel from the forward edge of the stem to the aft edge of the stern post.

Luff The forward edge of a sail.


Mast step The structure members that support the heel of the mast or compression post where the mast is stepped onto a deck or coachroof.

Mouse Secure a shackle or other fitting with wire or cord to prevent it coming undone.. Mouse is pronounced with a "Z" as in the Cornish village Mousehole.


Overplate On a steel vessel, plating fitted on top of the hull plate.


Parrel A movable loop or collar, used to fasten a yard or gaff to its mast.

Paying The compound used to fill a seam, often between planks forming the hull.

Pintle The pin or bolt on which a rudder pivots. The pintle rests in the gudgeon.

Port The left side of the boat when facing the bow.


Rabbet A groove cut in wood to form part of a joint, also know as a rebate.

RIB Rigid inflatable boat; a fast craft with a rigid, planing hull usually made of GRP or aluminium with inflatable an inflatable collar.

Rubbing strake A moulding fitted to the outside of the hull, usually at deck level, to protect the topsides.

Rudder nib On narrowboats, the extension to the rudder above the waterline.

Rudderstock The bar, tube or post connecting the rudder vane to the steering mechanism.

Rudderstock tube A tube in the hull through which the rudderstock passes.

Running rigging Rigging used to hoist and set sails.


Sacrificial chine On a narrowboat, an extension of the bottom plate to provide protection and a wear edge for the chine.

Sampson post A strong post often used as a mooring point.

Saponification Production of an alkaline metal soap that can damage some paint coatings, often as a result of electro chemical activity.

Scantlings Dimensions of a vessel's structural members

Scuppers Holes cut in the hull side or toe rails allow water to drain from decks.

Seacock A valve in the hull of a boat.

Sheer The concave curve of the deck line from the bow to the stern..

Shrouds Standing rigging from a mast to the sides of a sailing vessel.

Skeg A downward or sternward projection from the keel in front of the rudder. In some craft the skeg has a bearing that supports the rudder.

Skin tank In narrowboats, a steel tank welded to the interior face of the hull. The skin tank forms part of the engine cooling system; coolant passes through the tank and is cooled by contact with exterior hull plating.

Spar A pole used to support rigging and sails.

Spreader A small fixed spar attached to the mast on a sailing boat that deflects the shrouds to provide better support.

Spurling pipe A pipe that feeds the anchor chain into the chain locker from the deck above.

Squat The effect where the stern of the vessel sinks lower into the water when forward power is engaged.

Stanchion The upright supports along the upper deck that carry the guard rails or wires.

Standing rigging The permanent fixed rigging such the stays and shrouds.

Starboard The right side of a vessel when facing the bow.

Steering flat The compartment containing the steering gear.

Stem The foremost structural member forming the bow and connected to the keel at the forefoot.

Stern The aft part of a vessel.

Stern gear The propulsion equipment aft of the gear box, including shafts, shaft couples, glands, shaft tubes, struts and propellers.

Stern tube The tube through the hull through which the propeller shaft passes.

Superstructure The structures on a vessel that project above her main deck, not including masts and rigging.

Stringer Internal structural member that runs fore and aft.

Swan neck On a narrow boat, the S-shaped steel bar that connects the rudder stock to the tiller.

Swim On a narrowboat, the underwater section of the hull side that reduces in beam to allow water to flow to the propeller.


Tabernacle A bracket which allow a mast to pivot so that it can be raised or lowered.

Tack The forward bottom corner of a sail.

Tingle A temporary patch on the hull, often a made as an emergency repair. It has been known for tingles to remain in duty for many years.

Tiller a lever used for steering, attached to the top of the rudder post. Used mainly on smaller vessels, such as dinghies and rowing boats.

Timber A stem-bent frame.

Toe rail A low strip running around the edge of the deck that helps the crew keep their footing.

Top strake On a narrowboat, the upper part of the hull side.

Transom The aft board of the stern, which is more or less flat.

Trim tabs Horizontal plates usually attached to the transom of a motor boat that allow the pitch of the vessel be adjusted in response to the squat effect.

Tumblehome A description of hull or cabin form where the widest part reduces higher up when viewed in a transverse section.

Turnbuckle See bottlescrew.


Uxter plate On a narrowboat, the plate that forms the bottom part of the counter and lies parallel to the bottom plate. It is also known as the counter bottom plate.


Weedhatch An opening in the uxter plate of a narrowboat directly above a propeller, allowing a fouled propeller to be cleared while the boat is afloat.