Lock Function Selection 2026: A Decision Table by Room Type, and the Two Questions That Settle Every Opening

Most lock function errors are not made by people choosing badly between options. They are made by people who never realised a choice existed, ticked the default, and found out at handover.

The whole decision reduces to two questions, and they are worth asking in this order because the second one outranks the first.

The two questions

**Who is allowed through from outside?** Everybody, some people with a key or credential, or nobody.

**What happens to the person already inside?** This is the life-safety question, and it is the one that overrules any convenience argument. On almost every opening in almost every jurisdiction, somebody inside must be able to get out **without a key, without a code, and in one motion**.

Any function that fails the second question is wrong even when it answers the first perfectly. A storeroom that locks securely from the corridor and also locks somebody in is not a secure storeroom; it is a hazard with a good cylinder.

The decision table

Read it by room, then check the function against the two questions above before you write it into a schedule.

The three errors that are life-safety problems, not inconvenience

**A double-cylinder deadbolt on an occupied-space escape route.** A deadbolt keyed on both sides needs a key to get out. It is sometimes specified on a glazed door to stop somebody breaking the glass and reaching the thumbturn — a real threat, answered in a way that can trap people. Where the glazing risk is genuine, the answer is laminated glass or a different lock, not a key on the inside of an escape route.

**Storeroom function chosen for a room people work in.** Storeroom is correct precisely because its outside trim is always locked. It is wrong the moment the room becomes a place somebody spends time in with the door closed and a colleague pulls it shut behind them — not because it traps them, but because it generates a culture of propping the door, which then defeats a fire door.

**Any function added after the fire test.** If the opening is a fire door, the lock is part of a tested assembly, and a function change that alters the latch is a change to the assembly. Our fire door hardware page covers what that means for the certificate.

Passage is a function, not an absence of one

The commonest specification slip on a corridor door is leaving the function blank because the door does not lock. Blank is not a specification; it produces whatever the supplier's default is, and the default frequently has a keyway in it.

Passage means the latch holds the door closed and both handles always retract it. There is no cylinder, no turn, and nothing to lock. On a door that must never be securable — a fire escape route through an occupied floor — specifying passage explicitly is a safety decision, not a cost saving.

Privacy: what the outside emergency release actually is

A privacy set locks from inside with a turn or button and can be released from outside in an emergency, usually with a coin-turn, a small screwdriver slot, or a pin.

Two things get missed. The first is that the release has to be reachable and understood — a release that needs a tool nobody in the building owns is a release that will be answered with a crowbar.

The second is the indicator. On a WC in a public building, an occupied/vacant indicator does more work than the lock: it prevents the attempt rather than resisting it, and it is what stops a queue forming against a door somebody is behind.

Classroom function, and why it exists

It is the one function on the table that is not obvious from its behaviour, and it exists because of a specific scenario.

A teacher needs to secure a door against the corridor. With a storeroom or entrance function, they have to step into the corridor to use the key — which is the one place the threat might be. Classroom function lets the outside trim be locked and unlocked **from inside the room**, so the door is secured without anyone leaving it. The inside handle always retracts the latch, so the room can still be evacuated.

It is a function worth knowing by name, because a specification that describes the behaviour in words usually receives an entrance function and a note.

What our catalogue actually carries

Function counts across our 924 published products, from the specification rows themselves.

Read that honestly and it says something specific: **we are strong on entrance, privacy and passage, and we are not a broad institutional function range.** If a project needs classroom and storeroom functions across forty openings, we have one model of each and you should ask before designing around us.

Publishing that table is more useful than implying a full function set and discovering the gap at the schedule stage. The order-code suffix carries the function on the models that have one — `ET` entrance, `BK` privacy, `PS` passage — so `201 PBET` is model 201, polished brass, entrance.

What happens when access control arrives

An electronic credential does not replace the function decision; it adds a second answer to the first question while leaving the second question exactly where it was.

Access control decides who gets through from outside — a card, a code, a phone. It does not by itself decide what happens to the person inside, and that is still governed by the mechanical function of the lock and by the requirement that egress be free, immediate and needing nothing.

So the failure to watch for is a project where the electronics answer question one so convincingly that nobody re-asks question two. An electrically locked door on an escape route needs a mechanical path out that works when the power, the network and the server are all gone, because those are exactly the conditions a building is evacuated in.

Three things to settle at specification stage rather than at commissioning.

**Fail-safe or fail-secure, per opening.** Fail-safe unlocks when power is lost; fail-secure stays locked. Which is correct is a life-safety and security decision for that specific door, and two doors in the same corridor can legitimately be opposite. It is not a product preference and it is not a site decision.

**What the mechanical override is, and who holds it.** Every electronically controlled opening needs a way through when the system is down. A key that exists in a drawer nobody can find during an evacuation is not an override.

**Whether the door is a fire door.** An electric strike or electrified lock on a fire door has to be suitable for that use, because the hardware is part of what keeps the leaf latched, and a fire door that does not latch has failed. Our fire door page covers why this is a certificate question rather than a product question.

The mechanical function stays on the schedule either way. A card reader on a storeroom door does not turn it into a passage door, and writing only the reader into the schedule leaves the lock itself to a default.

What to write on the schedule

The function by name, not by description. "Locks from the corridor" is a behaviour that three functions satisfy differently.

The egress requirement explicitly, even when it feels obvious. A line that says "free egress, no key inside" survives a substitution; a line that assumes it does not.

Whether the opening is a fire door, because that constrains the function before any other consideration.

And the handing and finish code, because a function is only one of the six values an order needs to be complete.

A schedule that names the function, the egress requirement and the fire status leaves nothing for a default to decide. That is the whole job of the document, and on this category it is worth three extra words per line. The alternative is a building where somebody decides each of those at the moment of installation, without knowing what the room is for, and nobody finds out until the first time the door is used the way it was not planned for.