Abstract: A conventional wooden door (1) is generally provided with a handle (29) activating a latch from closed to open position and a latch knob (30) activating a bolt between closed and open position. The latch and bolt enter recesses provided in the frame flange (15) and for this reason it is relatively easy to break open a door (1). This is made more difficult if a body (2) is arranged on the inside of the door, said body (2) being provided with spring bolts (17 and 18) and dowels (23 and 24) to fit into recesses (19, 20) in the relevant jambs (16, 11, repectively).