For added door security, both FUHR 856 and 859 door locks can be supplied with an integral restrictor. When engaged, the use of the product restricts the opening of the door to just 100mm, a function achieved traditionally by door chains. The FUHR restrictor is engaged and released by turning the small additional thumb turn handle on the inside of the door. In order to open the door to allow entry, the door needs to be closed fully and the restrictor disengaged. The restrictor mechanism is fully concealed when the door is closed.

The FUHR restrictor can be used with individual keeps or as an integral part of a one piece keep.