This is a rim-locking system that bolts the door into the frame and offers a higher level of security.
A multi-point locking system has a minimum of three locking points that all lock simultaneously by the turn of a key.
These are most common on patio or French doors - typically uPVC doors - and less common for main entrance points.
The bolts are normally operated by lifting the door handle from either side of the door leaf and are locked in place by the turn of a key from either face of the door or, if the door is the only means of escape, by an internal thumbturn. The compression bolts, if fitted, and or the hook bolts pull the door tightly into the weather seals in the frame to keep it weather tight.