Master keying Master keying and access control are powerful and flexible methods of ensuring a high level of security, but their complexity often deters clients or results in a less than optimal solution being chosen. In its simplest form a master key system allows each key holder to access pre-designated doors within a building. We have been designing and supplying ASSA master key systems for over 50 years. The formidable level of expertise developed by our specialist Locking Systems Department is at your disposal. Using the latest software and equipment we can develop a system tailored to meet your specific requirements quickly and easily. Our national network of ASSA Security Centres can assemble and supply systems that are tailored to meet your own security needs, while leaving the flexibility to adapt to future changes.