In standard one-way action, dead bolt thrown or withdrawn by key from the outside and withdrawn by lever or turn knob from inside using a single cylinder (not supplied) or thrown or withdrawn by key from either side and withdrawn by lever handle or turn knob from inside using a double cylinder (not supplied). In two way action, deadbolt may additionally be thrown by lever handle or turn knob from inside. Pierced to accept 20mm and 38mm centre bolt through fixing escutcheons. Deadbolt is brass with two hardened steel rollers and the throw is 13mm. One way action as standard and two way available on request. The measurements are as follows: 76mm(A) lock comes with 57mm(B) backset and 72mm(C) centres, 101mm(A) lock comes with 82mm(B) backset and 72mm(C) centres