Glossary of Terms

If you are new to boating we hope you find the following glossary helpful. We have tried to limit it to those terms you are likely to come across when reading our details of boats for sale.

Collated & edited by Trines Ward

air draught (or draft)
The overall height of a vessel measured from the water line to the highest fixed part of the superstructure. It is necessary to know this when on rivers subject to raised water levels to ensure you can safely pass under low bridges.

anode (or sacrificial anode)

In steel boat terms: – replaceable, large piece of metal e.g. magnesium, fitted to hull under the waterline, designed to corrode due to electrolysis instead of the hull.  2-year inspection for wastage/possible replacement is usual at which time it is normal to clean the hull and apply blacking. Narrowboats normally have 2 or 3 each side of the hull.

bed cupboard
Distinctive and often highly decorated cupboard in boatman’s cabin fitted on port side between table cupboard and engine room bulkhead. Has tall door hinged along bottom edge that lets down to become a cross-wise small double-bed board, the mattress being stored in the cupboard.

(1) The bunk or bed in a boat. (2) The space occupied by a vessel when tied up.

The line along the hull sides where sides and bottom meet.

bilge pump
A pump (electric or manual) for removing water that has collected in the bilges.

Strictly, the ‘air space’ inside a boat’s hull lying beneath the level of the port and starboard bilge lines but usually applied to the whole region beneath the cabin floor or decking no matter where it is in relation to the bilge line.



Term for protective coats of, often bitumen based, paint applied to steel hulls to discourage rusting. Current practice requires blacking at least every two years.

boatman’s cabin

Originally the after-cabin (approx. 8′ long) of a working narrowboat, providing the crew’s living and sleeping accommodation. Often recreated in modem traditional-style narrow boats in addition to the main cabin accommodation.

The foremost part of a vessel’s hull (“fore-end” is word preferred by working narrowboatmen).

bow thruster
Steering aid transversely mounted in bow section giving, from a small propeller, thrust on demand to either port or starboard.  Powered electrically by battery or alternator, or by hydraulic motor.

BSS Boat Safety Scheme

All boats require a safety inspection certificate every 4 years from an approved surveyor. Whilst this covers safety items such as ventilation, fire, gas & electrical hazards, buyers of boats should not rely on certificate as proof of sea-worthiness or good engine condition.

Upright panels (or ‘walls’) separating a boat into compartments.

Small round porthole set in the cabin-top fitted with convex glass, for lighting the cabin rather than for seeing through.

The superstructure of a narrowboat

Rails or strip plinths that edge the fore-deck and counter of traditional-style narrowboats, now usually made of steel and purely aesthetic, but originally applied as a replaceable timber edging to take wear and tear.

cassette toilet
A simple chemical toilet ranging from a small portable boxed bowl with a removable storage cassette underneath up to larger, fixed, electric-flushing, swivel-bowled versions with larger cassettes. A feature is ease of emptying without charge at the many sanitary stations along the canals.

Where hull bottom and hull sides are flat surfaces, as in most narrowboats, the chine is the sharp edge where they meet.

Open area, usually set lower than surrounding side-decks, used for sitting-out and for storage.


The round or elliptical (looking from above) small stern deck of a narrowboat, forming a ledge projecting over the propeller and shaft.


Optional assembly over the forward cockpit of a modern narrowboat. Based on a solid or glazed triangular deckboard or ‘cratch-board’ which is supported from the cabin-top by a ‘top plank’. The assembly is completed by a fitted soft cover. The result greatly extends the usability of the cockpit.

cross bed  
A double bed across the full width of the boat. The foot folds or slides away sufficiently to form a gangway through during the day. Some 3 – 6 inches shorter than standard sized beds.

cruiser stern/style  
A modern narrowboat with a large, exposed but more sociable aft deck, protected by taff rail, under which is the engine compartment.

deck equipment

Collective term for the boat-hook, shaft, gangplank, ladder etc.

Cabin ceiling. In strict nautical terms, it is the underside of a deck.

dog box

An arrangement of, usually upholstered, bench seats with storage under & a demountable table to facilitate eating (eg ‘L’-shaped, Pullman style etc) and which can also be lowered to form a bed.

A timber-framed fixed or openable double-pitched glazed skylight on roof, very much larger in plan than a pigeon box.

The maximum underwater depth of a vessel’s hull, normally aft underneath the rudder, at the skeg.

Deck fitting to guide ropes and reduce wear, frequently fitted amidships to protect paintwork from centre-line.

A raised lip or rail around the edge of a shelf, table or other horizontal surface to prevent objects from sliding off due to motion of boat.


The higher level deck area in the bow of a vessel; in a narrowboat, often over the forward gas locker.

The lower level deck area, immediately behind the fore-deck, sometimes with a cratch & fitted cover over.

Height of deck above water level, measured to the lowest place of possible entry, perhaps to scuppers or to engine compartment ventilation grilles if in hull sides.

galvanic isolator
A fitting to a boat’s electrical system, intended to help prevent galvanic corrosion to the hull but opinion is divided on whether these are effective. Such corrosion is serious so it certainly does no harm to have one, at least it helps you to sleep more soundly!


A common misspelling of ‘gunwale’ – see next entry

The wale or upper edge of the hull were it joins the cabin side (pronounced ‘gunnel’). It is spelled by some as ‘gunnel’ which the collator feels is very wrong; the word ‘wale’ is Old English for ‘ledge’ or ‘plate’ and early sailing ships had a reinforced wale constructed around the upper deck to take the weight of cannons, hence ‘gunwale’.

holding tank

An on-board storage tank for toilet waste, emptied by vacuum at pump-out stations.

The main part of the boat that sits in the water and gives a boat its buoyancy. In steel narrowboats it is essential to slow corrosion and pitting to hull by regularly re-blacking, replacing worn anodes and to touch up damage to all external paintwork when it occurs.

Electronic device, common on modern narrowboats with no onboard AC generator, for taking power stored in the service battery bank and converting it from 12v DC to 240v AC for intermittent use of low wattage mains appliances e.g. TV’s, vacuum cleaners etc.  Quality of supply can be poor making it unsuitable for some sensitive electric motors and electronic equipment.

keel cooled
Method whereby sealed water-coolant system is cooled before return to the engine block by passing in fine tubes through a radiator attached to the inside skin of the hull below the water line.  Avoids the blockage problem inherent in raw water cooling system.

macerator toilet
A pump-out toilet where the waste matter is reduced to a slurry by blades in an intermediate tank before being pumped (by vacuum or water pressure) to the boat’s holding tank which can be anywhere within the hull

monkey box
Timber storage box with hinged lid fitted at aft end of side-bed in a traditional-style boatman’s cabin. Believed so-named after a make of brass polish.

navigation lights
Lights required, under international regulations and by various navigation authorities, to be shown at night or when visibility is poor.   White light forward required to be visible through 180º but very few canal boats comply in practice, often relying on their tunnel light (usually a car spot or fog light).   Port (red), starboard (green) and stern (white) lights not yet required on canals but are on most rivers.

pigeon box  

Decorative and functional means of ventilating the engine room or other cabin through a rectangular hole in deck-head, framed by wood or steel box sides and covered by roof-like double-pitched hinged lids that open upwards. Can have little portholes which then also make it a skylight.

port or port side

Left-hand side of boat when looking forward or the area away from the boat on that side.

pram canopy
Cloth canopy fitted on folding framework allowing it to be easily raised and lowered, fitted over a narrowboat’s counter to protect steerer from bad weather.

pump-out toilet

Toiletting arrangement where the waste matter flushes from the toilet bowl into a tank where it collects until it is pumped-out at a canal-side facility.

R.C.D./Recreational Craft Directive –
E.C. inspired mandatory standards for the construction of new boats and for builders to maintain supporting technical documentation. The initial certificate lasts for 4 years, after which boats must be examined to ensure that they have not been altered or that they comply with the Boat Safety Scheme.

raw water cooling   
System of engine cooling constantly taking cold water from canal or river through hull via sea cock and mud box, passing it through either a heat exchanger in a sealed water system, or through the engine block’s actual waterways – and expelling it warmed via a hull fitting above the waterline.  Beloved by many traditionalists but has disadvantage on inland waters of becoming blocked by mud, weed and rubbish. (As opposed to keel cooling).

remote greaser
A metal cylinder fitted close to the stern tube, acting as a reservoir for the frequent supply of grease to stern gland (or stuffing box).  Grease is forced from cylinder by hand-operated piston, through intermediate tubing into gland, reducing wear on the propshaft and helping to stop water ingress.

roses and castles
Traditional and highly stylized manner, along with simple geometric shapes and playing card suit symbols, of decorating a narrowboat’s cabin exterior and interior, doors, deck equipment etc. Close up the roses seem almost diagrammatic and each should comprise of no more than four colours.  The castle is the main element of what is called the ‘landscape’

rubbing strakes
Reinforcing steel strips attached to the hull of a boat to lessen damage to the sides.

Painted graining on cabin wood work or onto steel to make it look like wood – interior or exterior.

Holes through hull sides for draining decks, gas lockers etc.


(semi-trad) stern/style
A style of pleasure narrowboat based on the lines of former working boats but with a larger, more social, aft deck behind the accommodation which is surrounded with high side plates that continue the line of the cabin superstructure so that, when viewed from the sides, it looks like a traditional-style.

single lever control
A hand lever combining the functions of both gear operation and throttle control. Commonly called a Morse after a particular manufacturer.

speedwheel control
A wheeled control operating engine throttle through a series of revolving rods, usually coupled with a ‘push me – pull-me’ rod operated gear lever. Often to be found on traditional narrowboats with a vintage style engine in its own room forward of a boatman’s cabin.

Type of pleasure narrowboat, usually of short length, formerly constructed by Springer Engineering of Market Harborough. The first company to build narrowboats along ‘production lines’.


When looking forward, the right-hand side of the boat or the area away from the boat on that side. (Derived from steerboard, being that side of ancient sailing ships on which the steering paddle was situated).

(1)The foremost part of the bow of boat. On a narrowboat it is normally the curved vertical post into which the bow ends of the hull sides are welded.  (2) Also the practice of using the bow to push against an object – as in pushing open lock gates (frowned upon), or driving against bank when turning boat round (winding), or holding a boat on station under engine power against a flow of water (“stemming the tide”) or having a head-on collision with something (e.g ‘stemmed the bridge’).

The aft, or rear, end of a boat.

stern gear

Collective name for the propeller, propeller shaft, stern tube, gland & greaser etc

stern gland

An arrangement – usually by means of greased packing in a stuffing box – whereby water is prevented from entering a vessel at the point where the propeller shaft passes through the hull and also helping to reduce propshaft wear. A greaseless, water-lubricated gland is also in use that draws canal water through pipework & gland by propeller action. Intended as “maintenance free”, care is needed to clear the pipes of water when leaving boat in winter to avoid freeze damage.

swan’s neck

Name for the curved, ‘S’-shaped steel bar that connects the top of the rudder to the tiller.

(1) The tapers at forward and aft end of a narrowboat’s hull sides – from full hull width to stem post or to stern post. (2) A boat is said to swim well or to be a good swimmer  if it answers quickly and positively to the tiller and makes way without causing too much turbulence.

table cupboard
Distinctive and often highly decorated cupboard in boatman’s cabin fitted on port side between stove and bed cupboard. Has tall door hinged along bottom edge that lets down to become a table top. Sometimes featured in main cabins of modern narrowboats due to its space saving properties.

taff rail
Guard rail wholly or partly around aft cockpit or counter, usually high enough and wide enough to sit on.

ticket drawer
Very small drawer or cupboard just inside the aft doors of a narrowboat originally used for keeping receipts for tolls incurred, cargo manifests etc. Often present in modern trad-style boats.

tiller bar
Lever, connected via swan’s neck to the rudder, against which the steerer pushes to steer the boat. Usually removable.

Hull surface above waterline.

traditional-style/trad stern
A style of pleasure craft based on the lines of former working narrowboats in which the stern counter, only up to 3ft astern of the accommodation, extends over the propeller, and the tiller is arranged so that the steerer stands in the hatchway within the aft doors of the cabin.

A cross-beam or vertical bulkhead between the hull sides, used to strengthen stern of boat.

A generally shorter length boat with no cargo space but with an often powerful engine for towing other boats, hoppers etc. A modern tug-style pleasure boat has a long, raised front deck with storage beneath and/or a double bed that pulls out into the forward cabin.

tumble home
Angle, occasionally very pronounced, at which the cabin side of a narrowboat leans in, when seen end-on, to help cabin top from scraping bridge & tunnel arches. Most narrowboat hull sides also tumble home – with slight lean-in from top rubbing strake to the gunwale; and from the top rubbing strake down to the chine.

tunnel light

Traditionally a low intensity oil or candle lamp shown at the front of a narrowboat when navigating tunnels, more as a warning to oncoming boats than as a steering aid.  Replaced by a car headlight when boat electrics introduced but always angled upwards to avoid dazzling on comers.  A motor might also have shown a small light (or “bobby dazzler” at the stern or from the back of the cabin-top for the benefit of the butty steerer behind.

uxter plate

The steel bottom plate of a narrowboat’s stern counter deck where it project over the propeller & rudder.

A mooring or towing rope or the rope part of the cable attached to an anchor.

A hatchway, with a watertight lid, through the counter of a narrowboat providing access from deck level for clearing a fouled propeller.

well deck
The floor of a well or cockpit.

wind dodger
Weatherproof fabric curtain stretched around between taff rail and deck to provide shelter, and to prevent infants or animals from falling overboard from the cockpit or counter.

(1). L-shaped handle for operating lock paddles. Has a square socket at one end to fit on the spindle operating the paddle gear.  Also known as a ‘crank’ in some districts. Often called a ‘lock key’. (2) Drum winch with cranked handles or removable hand spikes used for raising an anchor.