The KSP is a spring loaded version of the Castell K Lock using an internal spring to automatically extend the bolt to the full extend position when permitted to do so. The KSP lock is a key operated mechanical bolt interlock that is suitable for the control and locking of mechanisms. The standard unit comes with a 15.88 mm diameter bolt that is used to lock movement. The bolt is retracted against the spring by turning the key. This process enables automatic release of the key under certain permitted conditions.