Interchangeable core (IC) offers maximum flexibility to the building owner. Whenever a key is lost or stolen, locks can be rekeyed quickly by non-locksmith personnel. All it takes is the special “control” key. This key is used to remove and install all cores in the system. Just go to the door, remove the old core and install the new one with the control key. Security is regained in seconds! Unlike most other brands, PDQ interchangeable cores can always be integrated into existing systems with no adverse effect on the key system.