Product Code: SP1082. The Jackloc window and door restrictor was designed with Health and Safety in mind. This was due to the number of restrictors failing and accidents occurring, sometimes resulting in fatalities. Exceeding the demands of the British Standard BS6375 Part II Test 6 to a level of 1,520 Newtons, the Jackloc restrictor can be fitted to any style of window and any window material including slim line steel W20.