Contract Door Security Bolt, also known as a Rack Bolt. This bolt is morticed inside the door edge and can be locked or unlocked using a separate splined key or a fixed splined turn. The bolt features an internal sawtooth rack mechanism that engages with the splined key, creating a gearing action to smoothly operate the bolt. Keys are sold separately. Available Finishes: Polished Chrome, Satin Chrome, or Electro Brass. Dimensions: 85mm, 57mm Centres. Supplied with both radius and square keep plates. The Hex/Rack Style Keys required to operate these door bolts are sold separately; please see related products below.