Subframe

The subframe is the frame that is anchored to the wall before the door is fitted, and to which the door frame is fixed afterwards. On security doors it is usually made of metal and is secured into the wall with fixing lugs or anchor bolts.

You cannot see it, because it is hidden by the frame and the architrave, but it is what holds the whole assembly up. A very good security door fitted on a loose or badly anchored subframe can be levered out in one piece without touching the lock.

So when you have a front door fitted, it is worth asking how the subframe is done as well as which lock it has. If you want to replace your door, it is the first thing we check: you will find it in security doors.