A contract door security bolt is sometimes called a rack bolt. This bolt is morticed inside the door edge and can be locked or unlocked via a separate splined key or with a fixed splined turn. The bolt has an internal sawtooth rack mechanism into which the splined key is inserted. The spline engages with the rack teeth and forms a gearing action that smoothly operates the bolt. Splined key or turn to be ordered separately. Comes with a 5-year mechanical guarantee. Suitable for use in all domestic, industrial, and commercial environments.