Reference

Glossary

The words that turn up on listings and specification sheets, in plain terms. Several of them describe a trade-off rather than a feature, and those are the ones worth reading twice.

26 terms, 26 of them cross-referenced to each other.

Backset

The distance from the edge of a door to the center of the hole the lock sits in. Two values are common on American residential doors, and a lock made for one will not reach the strike in the other unless it is adjustable. Measure to the middle of the hole, not to its near edge.

See also Bore and cross bore, Strike plate

Bore and cross bore

The bore is the large round hole drilled through the face of a door for the lock body. The cross bore is the smaller hole drilled in from the door edge, where the latch or bolt assembly sits. A replacement lock has to cover the existing bore or you are into filling and re-drilling.

See also Backset, Deadbolt and latch

Strike plate

The metal plate on the door frame that the bolt or latch enters. On a lot of homes it is fixed with short screws that stop inside a thin jamb board, so the load goes into trim rather than framing. Replacing those screws with longer ones is the cheapest meaningful change most doors can have.

See also Deadbolt and latch, Backset

Deadbolt and latch

A latch is the sprung tongue that holds a door closed when you pull it shut; a deadbolt is a solid bar you throw deliberately and which does not retract under pressure. They do different jobs and a handle set with a latch is not a substitute for a deadbolt. A deadbolt only counts when it fully engages the frame.

See also Strike plate, Single and double cylinder, Mechanical override key

Single and double cylinder

A single-cylinder deadbolt has a key outside and a thumbturn inside. A double-cylinder deadbolt takes a key on both sides, which means anybody inside needs a key to leave through that door. Whether double-cylinder locks are permitted on a dwelling exit depends on the code your jurisdiction has adopted.

See also Deadbolt and latch, Egress

ANSI/BHMA grade

A published performance classification for builders hardware, developed under the American National Standards Institute process and administered by the Builders Hardware Manufacturers Association. A grade belongs to a specific tested product and is published by its manufacturer. It cannot be inferred from weight, finish or a seller using the word certified.

See also Deadbolt and latch, Strike plate

Keyway

The shaped slot a key enters, and the profile that decides which keys will physically go in at all. Locks from different manufacturers usually use different keyways, which is why a house rarely ends up with one key for everything without deliberate effort.

See also Rekeying, Mechanical override key

Rekeying

Changing the internals of an existing lock so old keys no longer work, without replacing the lock itself. It is usually cheaper than a new lock and it is the answer when the question is who might still have a key rather than is this lock any good.

See also Keyway, Deadbolt and latch

Bump key resistance

A property some lock cylinders are designed and marketed to have, relating to a known category of attack on pin tumbler locks. This site does not describe how any such attack is performed. Treat the term as a feature claim on a listing, and check whether the manufacturer has published anything to support it.

See also ANSI/BHMA grade, Keyway

Egress

Getting out. In home security it is the counterweight to everything else: hardware works by making an opening harder to use, and escape depends on the same opening staying easy to use. Every restraining device on this site is described alongside that trade-off.

See also Emergency escape and rescue opening, Window opening control device, Single and double cylinder

Emergency escape and rescue opening

The term model building codes use for an opening in a sleeping room that somebody can get out through and a firefighter can get in through. The property that matters most is that it opens from inside without a key, a tool or special knowledge. Exact dimensions are set by the code your jurisdiction has adopted.

See also Egress, Window opening control device

Window opening control device

A device that limits how far a window opens but releases from inside when the opening is needed. The concept exists because limiting a window and blocking a window are different things. It is the shape any stop on a bedroom window has to have.

See also Emergency escape and rescue opening, Egress

PIR sensor

A passive infrared sensor, which triggers on changes in heat across its field rather than on movement in an image. It is what most battery cameras and lights use to wake up, and it explains why a warm car, a pet or a sunlit wall can set one off while a person at the wrong angle does not.

See also Field of view, Package detection

Field of view

How wide an angle a camera sees, usually quoted in degrees. Wider means more of the porch in frame and less detail on any part of it, and faces at the edge of a very wide lens are distorted. It is a trade, not a specification where bigger is better.

See also Bit rate, PIR sensor

Bit rate

How much data a camera uses per second of video, which decides how much detail survives compression. A 2K camera at a low bit rate can look worse than a 1080p one at a high one, particularly on moving subjects at night. Listings rarely quote it, which is worth knowing when comparing resolutions.

See also Field of view, Local storage

Local storage

Recording to a card or a base unit in the building rather than to a service. Nothing recurring, and nothing depending on an account staying active. The failure mode is that the recording is in the same building as the thing being recorded.

See also Cloud storage, Subscription tier, Bit rate

Cloud storage

Recording to a provider’s service, so footage survives the camera itself being taken. It lasts as long as the account and the plan terms allow, and both of those can change. Where a listing describes cloud history, read what it says about how long clips are kept.

See also Local storage, Subscription tier

Subscription tier

A level of a provider’s plan that determines what a camera can do beyond live viewing — typically history length, number of devices and detection features. This site does not quote plan prices anywhere, because they change; what it records is whether a listing states that recording requires a plan.

See also Cloud storage, Local storage

Two-way talk

A speaker and a microphone in the camera, so you can hear and be heard. It is genuinely useful for telling a courier where to leave something. It also means the device is recording conversations, which is handled separately from video in many places.

See also Chime, Tamper alert

Chime

The thing that actually rings inside the house. It can be the original wired unit, a plug-in wireless one, or a phone notification. A doorbell that only rings on a phone is a doorbell that does not ring when the phone is face down on a sofa.

See also Transformer, Two-way talk

Transformer

The component that steps mains voltage down to the low voltage a wired doorbell runs on, usually hidden near the consumer unit or in a hallway. A wired doorbell will only work if the transformer meets the requirement stated for that unit. Anything involving the mains side of it is an electrician’s job.

See also Chime

Mechanical override key

A physical key that opens an electronic lock when the batteries are flat or the electronics fail. Where a listing states one is included, that is what stands between a dead battery and a locked-out evening. Where a listing says nothing about it, assume there is not one.

See also Deadbolt and latch, Auto-lock, Keyway

Auto-lock

A setting that throws the bolt automatically a set time after the door closes. It closes the gap left by a household that forgets, and it will also lock you out while you carry the second bag to the car. Set the delay to match how the door is actually used.

See also Geofencing, Mechanical override key

Geofencing

Using a phone’s location to trigger something — unlocking as you arrive, arming as you leave. It depends on the phone having location permission, battery and signal, so treat it as a convenience rather than as the thing the door relies on.

See also Auto-lock, Tamper alert

Tamper alert

A notification sent when a device is moved, opened or removed from its mount. It is a useful signal precisely because it fires for something nobody has a legitimate reason to do. It is also the alert most likely to fire when you clean the porch.

See also Package detection, Geofencing

Package detection

Software that distinguishes a parcel appearing in frame from a person or a car, and alerts separately. Its value is timing: an alert while somebody is home means the parcel comes inside minutes after it arrives. It does not detect a parcel being taken any better than ordinary motion does.

See also PIR sensor, Tamper alert