The instinct behind early fitting is sound: an open site invites theft, and a locked door stops it. What the instinct misses is that two separate jobs are being treated as one. The first job is preparing the door for a particular lock, which has to happen early because it involves cutting timber. The second job is installing the cylinders and keys the owner will live with, which should come at the end because they decide who can get in for years.

When both jobs occur on the same day, the keyed cylinders remain in service throughout the build. Keys get copied for trades, left in utes, hung on hooks in site sheds and passed between subcontractors. None of that is anyone being careless; it is how a build runs. By handover, nobody can say with certainty how many working keys exist.

The opposite mistake causes its own problems. A builder who leaves every hardware decision until the end can find that the doors were bored for a lockcase that does not suit the lock the owner wants, or that a glazed front door has a stile too narrow for the chosen lock body. The sequence that avoids both problems is simple to state: choose early, prepare early, install late.

A mortice lock sits in a pocket cut into the edge of the door. The size of that pocket is set by the lock body, and the position of the key and handle holes is set by the backset, which is the distance from the face of the door edge to the centre of the spindle hole. Once a door has been prepared for one lockcase, swapping to a body with a different backset or a larger case means filling, re-cutting or replacing the door.

Glazed entry doors narrow the choice further. The usable width is the solid timber or aluminium between the door edge and the glass or moulding, and the lock body plus its furniture has to fit inside that strip. A wide-stiled solid door accepts almost anything; a slim-stiled glass door may only take a narrow-backset lock.

The cylinder adds another set of measurements. A Euro-profile cylinder is ordered to suit the thickness of the finished door and the furniture on each side, so it has to wait until the door and handle set are fixed. Key-in-knob and rim-mounted locks have their own hole patterns. None of these can be guessed later without risking a second set of holes in a new door.

The decisions that shape the doors belong at the design or ordering stage, well before any cylinder is keyed. The table below groups them by when they need an answer.

Deciding the cylinder grade early does not mean fitting it early. High-security cylinders are ordered to suit the key system, so knowing the choice in advance lets them be ready for final fix without holding up handover.

For internal doors, the decisions are lighter. Bedrooms, laundries and living areas need latches and handles chosen for the door thickness and the handle style, but none of them involve the key system.

The gap between hanging the external doors and handing over the house is where a temporary keying arrangement comes into play. The aim is a door that locks properly during the build, with keys that stop mattering the day the owner takes over.

There are two common ways to get there. The first is a temporary cylinder: a cylinder fitted only for the build, keyed to a set of trade keys, and removed at final fix when the owner's cylinder goes in. The trade keys are then useless because the cylinder they fit has left the house.

The second uses the owner's permanent cylinders with a built-in construction keying feature. The cylinder accepts a construction key during the build, and once the owner's key has been used, the construction key no longer operates it. The cylinder never comes out, and no tradesperson's copy carries over.

Which approach suits a rebuild depends on the hardware chosen and how many doors there are. A single house with three external doors can easily accommodate temporary cylinders. A rebuild into townhouses or units with shared entry doors is where a construction keying arrangement, planned alongside the eventual master key system, saves swapping hardware at every door.

Painting is the last messy trade through the house, and it is hard on door hardware. Paint and moving parts do not mix: coating that gets into a lock case, a latch faceplate or a cylinder face can stiffen the mechanism, and paint built up in the latch pocket or behind a strike plate can stop the hardware sitting flush. A clean paint finish depends on removing handles, plates, and strikes from the door and frame, which means any hardware fitted early is either masked or removed and refitted.

Every removal is a chance for screws to be lost, cams to go back in the wrong order or a cylinder to be refitted the wrong way round. Fitting the final hardware after painting gives a clean installation on a finished surface, with each part going on once.

There is also a security reason. Until the painter has finished, the house is still a work site with people coming and going. Once the painting is done, the list of trades who still need access shrinks sharply, making it the natural point to close off the build keys.

Final fix is the point where the locks the owner will live with go in. A clean sequence runs in this order:

A knock-down rebuild replaces a house, and the old house may have carried an original mortice lock or a rim latch on the front door. Some owners want that hardware kept for character. Older mortice locks can use cutouts that do not match modern lockcases, so a salvaged lock may require a door to be prepared specifically for it. If the owner wants to reuse period hardware, that decision belongs at the door-ordering stage too, with the old lock measured before the doors are made.

Other rebuilds go the opposite way. Where one site becomes two townhouses or a small block with a shared entry, the common doors and letterbox area need a key plan that works for every resident. A master key system, where each unit key opens its own door plus the shared ones, is designed before cylinders are ordered, because the whole set is pinned together. A single detached house with no shared doors needs none of that; keying the front, back, and side doors alike is enough.

Getting the timing right on a rebuild comes down to separating the choice from the installation. The choice shapes the doors, so it comes first. The installation decides who holds the keys, so it comes last, after the paint is dry and before anyone hands over the house.