Reference
The words on our specification tables, and what each one costs to get wrong.
These 23 terms were not chosen from a trade dictionary. They are the specification labels that appear most often on our own published product pages, counted — so every one of them is a field you will meet on this site, and the figure beside each entry is how many models state it.
373 published models state at least one of them. Each entry gives the definition first and the consequence second, because the consequence is the half that tells you whether this is the field you are about to get wrong.
Dimensions
- Backset145 models state it
The distance from the edge of the door to the centre of the spindle — the hole the handle turns in. 60mm is much the commonest figure in our range and a great many models are field-adjustable between 60 and 70mm; the full published span runs from 16 to 90mm. North America writes the same two figures as 2-3/8″ and 2-3/4″.
It is the single most common wrong number on a door-hardware order. A door already bored for 60mm will not take a 70mm lock: the handle lands in the wrong place and the latch does not reach the strike. Metal cannot be adjusted on site, so a wrong backset is a container that gets stored rather than fitted.
- Centre distance33 models state it
Our catalogue uses this label for two different measurements, and it is worth knowing which one you are reading. On a mortise lock case it is the distance from the cylinder centre to the spindle centre — we publish 45, 65, 68, 72, 85 and 92mm, of which 72 and 85 are the common European figures. On a pull handle or a glass-door fitting it is the distance between the two fixing points, and our range runs from 125 to 179mm.
On a lock case, the centres decide where the two holes go in the door face. Get them wrong and the cylinder hole and the handle hole do not line up with the lock — the door is scrap, not the lock.
- Door thickness170 models state it
The range of leaf thickness a product is built to fit. It is a range rather than a figure because the spindle and the fixing screws have travel in them.
Below the range the screws bottom out and the roses stand proud; above it the spindle does not reach through, and no amount of force will make it. This is the figure to check first on a glass or aluminium door, where leaves are thinner than the joinery a lock was designed around.
- Deadbolt throw44 models state it
How far the deadbolt projects from the lock face when fully thrown. Our published figure is 25mm.
The throw sets the depth of the pocket that has to be cut in the frame, and several markets write a minimum throw into the building code for entrance doors. A short throw in a deep-rebated frame leaves a bolt that can be levered.
- Projection17 models state it
How far the handle, bar or fitting stands out from the face of the door.
It comes off the clear width of a corridor, and on an escape route that width is regulated. A panic bar projecting 70mm into a 900mm corridor is a specification problem, not a preference.
- Standoff6 models state it
The gap between a pull handle's bar and the door face — the space your fingers go into. Ours are published at 18.5 and 26mm.
Too small and a gloved hand cannot use it, which matters on a cold-store or a workshop entrance. Accessibility guidance in several markets sets a minimum.
- Cross bore12 models state it
The large hole drilled through the face of the door that a cylindrical lock chassis sits in. Ours is published at 51mm.
A bore is a hole that already exists. A chassis larger than the bore means re-boring a hung door; a chassis much smaller leaves the rose covering nothing.
- Fixing centre5 models state it
The distance between the centres of the screw holes that hold a fitting to the door.
It is the figure that decides whether a replacement fitting lands on the holes already in the door. It is also the figure our catalogue is thinnest on, and we would rather say that than print an approximate one — ask, and we will measure the part.
- Glass gap5 models state it
The thickness of glass a patch fitting or glass-door lock is machined to clamp. Ours are published at 7, 7.5 and 8mm.
Toughened glass cannot be cut or drilled after tempering. A fitting that does not match the glass is a fitting that waits for a new glass panel, which is the longest lead time on the whole opening.
Mechanism
- Handing134 models state it
Which edge the door is hinged on and which way it swings, described from a fixed point of view so that two people can agree about it. Many of our models are reversible, which means the handing is set during installation rather than at the order.
Handing is the field most often filled in from memory, and the two conventions in common use disagree with each other. Where a model is reversible the question disappears, which is why it is worth checking before deciding rather than after.
- Chassis135 models state it
The working body of a cylindrical lock — the part that sits inside the cross bore and turns handle movement into latch movement. The trim bolts onto it from both faces.
Grade is a property of the chassis, not of the lever you can see. Two locks with identical handles and different chassis are different products, and it is the chassis that the cycle-life number belongs to.
- Latch87 models state it
The sprung bolt with one angled face that holds a closed door shut and pulls back when the handle turns. It is not a deadbolt: a latch can be pushed back, a deadbolt cannot.
A fire door has to latch, not merely close. If the latch does not engage the strike the leaf is held by nothing, and a door held by nothing is not a fire door however it is rated.
- Strike63 models state it
The plate let into the frame that the latch or bolt enters. Its lip guides the latch in as the door closes.
A strike fitted a few millimetres out is the usual reason a new door does not latch, and it is the cheapest thing on the opening to correct. The material matters on an entrance: a thin strike is what gives way first under force, not the lock.
- Spindle23 models state it
The square steel bar that passes through the lock and carries the turn of the handle from one side of the door to the other. Ours are 8mm and 9mm square.
8mm and 9mm look alike in a photograph and are not interchangeable — a 8mm spindle in a 9mm follower has play in it, and play becomes a handle that droops and then a mechanism that wears. Check the square before mixing a handle from one supplier with a lock from another.
- Cylinder105 models state it
The removable key-operated core. The cylinder decides the key; the lock case decides the function. Because it comes out without disturbing the lock, it is the part a master-key plan is written around.
A cylinder sized wrong for the door sticks out and can be gripped and snapped; sized short it does not reach the cam. The length is set by the door, not by the lock.
- Trim107 models state it
The furniture on the outside face — lever, knob, pull or plate — supplied separately from the device it operates. On a panic exit device the bar is the inside and the trim is the outside, and they are two order lines.
This is the most common misreading of our own catalogue, which is why fourteen records were renamed on 2026-09-14: a record called “035 Panic Exit Device” was the outside trim, not the bar. An order for the wrong one arrives as half a door.
- Rose18 models state it
The round plate behind a lever or knob that covers the fixings and the bore. Ours run 36 to 75mm in diameter, depending on the range — the catalogue calls it a rose on the handle ranges and a rosette on the knob and bathroom ranges, and they are the same part.
When a lock is replaced, the new rose has to cover the marks the old one left. A smaller rose on a refurbishment means filling and repainting every leaf.
Ordering and evidence
- Cycle life85 models state it
The number of open-and-close cycles the product completed in a laboratory test without failing. Our published figure is 200,000 cycles.
It is a test result, not a warranty and not a service life. It is comparable between products tested to the same standard and meaningless between products tested to different ones — which is the first question to ask when two suppliers quote the same number.
- Keying80 models state it
How a set of locks relates to a set of keys. Keyed different: every lock its own key. Keyed alike: one key opens a group. Master keyed: each lock has its own key and one key above opens them all.
A master-key plan has to be decided before the cylinders are cut, not after they arrive. Changing the hierarchy later means new cylinders for every door in the group — which is why the plan sheet exists.
- Function159 models state it
What the lock does rather than what it looks like: entrance (keyed outside), privacy (turn button inside, emergency release outside), passage (latch only, no locking), classroom, communication. The function is the last two letters of our order code.
Two locks that are visually identical can be a bathroom lock and an entrance lock. Specify a privacy set on a store room and it cannot be keyed; specify an entrance set on a bathroom and there is no way in when someone faints behind the door.
- Grade26 models state it
A performance class awarded by a test standard — ANSI/BHMA Grade 1, 2 and 3 in North America, EN 1125 and EN 179 for escape hardware in Europe. A grade always belongs to a named model tested as a whole assembly.
A grade is not a property of a factory or of a catalogue. If a supplier says the range is Grade 2, ask which model number the report names — that is the only form of the claim that survives a submittal.
- Finish287 models state it
The surface treatment, written as a two- or three-letter code in the middle of our model number — SSS, PB, SN, GM. It is the first half of the letters after the number; the second half is the function.
A finish code is not an ANSI/BHMA number, because a BHMA number also encodes the base metal: the same satin chrome is 626 on brass and 652 on steel, and supplying one against a specification for the other is a rejected submittal.
- Narrow stilea term, not a spec row
An aluminium door whose vertical frame member is too slim to take an ordinary mortise lock — commonly around 30 to 50mm of usable depth. It needs a lock case built for that depth rather than a standard one cut down.
Fitting a standard case into a narrow stile removes material the door was relying on, and the leaf sags within a season. The sag is blamed on the hinges and caused by the lock pocket.
A term we have not defined?
Send it. If it is a word on one of our own pages that is not here, that is a gap in this page rather than a question about the word, and we would rather fix the page. The two references beside this one answer the questions that come next: how our order codes are built, and what happened to a model number that no longer resolves.