When you turn the handle on your double glazed upvc door, it operates a metal strip, which extends more or less the full length of the door.

This metal strip is in turn connected to hooked bolts at the top and bottom of the door, and to mushroom or slider bolts, which interlock with receivers on the door frame.

The security advantage of the five-point of locking system is immediately apparent, as the door is secured at the centre, near the handle, at the top and bottom, and again halfway between them, providing a much greater resistance to forcing or jemmying.