Jamb

The jamb is each of the two vertical pieces that form the sides of the frame of a door or a window. The two jambs and the head at the top make up the lining that the leaf closes into.

Each jamb has its own job. One carries the hinges that hold the leaf. The other carries the strike plates, where the latch and the bolts go in. On doors with a multipoint lock there may also be strike plates at the top and bottom.

The jamb on the strike side is the one that suffers most when someone tries to lever a door open, and the one that shows it most when the timber swells. If you see the jamb splintered next to the lock or the strike plate loose, it may be a sign of an attempted break-in. What to do in that case is explained in attempted burglary.