A lock is a connection, not a barrier
The most useful way to think about a lock is as the link that ties the leaf to the frame. The more points it holds, and the deeper it holds them, the stronger the door. That reframes the shopping question: before brands, ask how many bolts throw, how far they travel into the frame, and how the keeps are built.
Cylinder locks
The standard today. The cylinder that takes the key is a separate component from the lock case and can be replaced on its own, which is why a lost key or a change of tenant means a new cylinder rather than a new door.
What matters in a cylinder is mechanical. Pin count and pin arrangement make keys harder to copy. Resistance to pulling and snapping comes from keeping the cylinder nearly flush and backing it with a reinforced escutcheon. Projecting more than 2 or 3 mm beyond the face of the leaf invites a pair of pliers, so cylinder length is chosen to match leaf thickness.
Lever and mortice locks
An older logic, where the key turns the mechanism in the case directly; still found on internal and storeroom doors, with the drawback that a lost key means a whole new lock. "Mortice" describes the mounting rather than the mechanism, and steel doors use it almost universally because the cavity protects the case.
Multi-point systems
The usual choice on external doors. Turning the key, or lifting the lever, throws bolts from the top, bottom and lock edge of the leaf. Two things improve at once: force is distributed instead of concentrated at one point, and the leaf is pulled evenly into the frame, so the gasket compresses properly and acoustic performance rises.
- Side bolts: the main throw from the lock case; depth of engagement in the keep is what counts.
- Vertical bolts: pins into the head and the threshold, which stop the leaf being flexed open.
- Hinge-side security pins: not locks, but they do the same job — the leaf stays in the frame even if the hinges are cut.
The wider the leaf, the more a multi-point system earns its cost. At building entrance doors width, single-point locking lets the centre of the leaf flex noticeably.
Electronic locks
Code, card, fingerprint and phone-operated systems do not replace the mechanical lock; they replace what triggers it. Underneath a well-built electronic lock there is still a case and bolts. Three questions before buying: how does the door open when the battery dies, is there a mechanical key override, and what is the working temperature and humidity range? For doors facing direct sun or coastal humidity, the last one decides whether the product survives its second summer.
Panic hardware
On escape doors the logic inverts — the door must open from inside with one push by someone who knows nothing about it. Pressing the bar retracts every bolt simultaneously. Nothing key-operated is left on the escape side; an outside lever is optional and depends on whether the door is used in both directions. For fire doors this configuration is confirmed before production, since adding it later means drilling a finished leaf.
Selection criteria worth using
- Bolt engagement depth, which can matter more than bolt count.
- Keep plates: a thin keep wastes a good lock, so it must be reinforced into the frame profile.
- Compatibility with leaf thickness, for both case and cylinder length.
- Duty cycle: a building entrance opened a hundred times a day is not an apartment door.
- Spare parts availability five years out, especially for export projects where a single failure otherwise idles a whole door.
Maintenance is cheap and mostly about not doing the wrong thing. Liquid oil and grease in a cylinder collect dust and eventually seize it; use a dry or graphite-based lubricant. If the key turns hard, check the door for sag before blaming the lock — a dropped leaf forces the bolts into their keeps. We can supply doors with cylinder, multi-point or panic configurations specified per opening; tell us the use and we will quote accordingly, shipping from Istanbul.