Key Lock Box

Instead of controlling a door, this holds a real key inside a steel box that opens on a code. Wall-mounted versions bolt through masonry with two or four fixings; shackle versions hang from a handle, a railing or a gate. Mechanical models use a dial or push buttons and need no power at all. Connected models add Bluetooth or Wi-Fi, one-time codes and a log of every open.

Where a Smart Deadbolt or a Keypad Deadbolt gives access without any key existing, a lock box is a workaround that keeps the original lock exactly as it is. That makes it the cheapest way to hand out access, and the least secure of the group, because the whole point is that a working key sits outside the building. Renters who cannot change hardware and owners of doors no smart lock fits use one for exactly that reason.

Holiday lets, house sitters, dog walkers, carers and estate viewings are the common cases. Keep one for the emergency spare so you stop hiding a key under a stone. Do not use one on a shared entrance or an obvious wall beside the door in a busy street. Never leave a code unchanged for months on a property strangers visit.

Steel gauge and mounting decide everything. Look for a body that resists prying at the lid seam, a shutter over the dial, and fixings that cannot be reached until the door of the box is open. Wall mounting into brick beats a shackle model, which can be levered or attacked away from the property. Some products carry an insurance-recognized security rating in their home market, so ask whether yours does, since some insurers will not cover a key left outside.

Change the code between guests every time, not just when it feels due. Rinse the keypad and hinge with fresh water in coastal air and oil the hinge lightly, because a seized lid is the usual failure. Mount it out of sight of the street, below eye height, and check the fixings once a year.