4530 Standard Duty Deadlatches provide flexible traffic control during and after business hours. Designed to retrofit into the prep of older MS1850 Deadlocks and discontinued 4250 Deadlatches. Function The 4530 Standard Duty Deadlatch offers flexibility of traffic control during and after business hours. A reverse turn of the key while the bolt is held retracted retains the bolt to allow two-way traffic for healthcare, financial institutions, retail, and other applications that require free entrance at certain times and exit-only at other times. 4530 Deadlatches are designed to fit without alteration, the stile cutout for older MS1850 Series Deadlocks and discontinued 4250 Deadlatches of same backset. Operation Turn key or operate handle to retract spring-loaded Latchbolt. To hold bolt retracted, push it in and secure by reverse turn of key. Lock accepts any standard 1" [25.4 mm] length, 1-5/32" [29.4 mm] diameter mortise cylinder with MS® cam such as the 4036 Mortise Cylinder or thumbturn such as the 4066 Thumbturn, available separately. Lock accepts cylinder from either or both sides. This listing: part 4533-35-IB 1-1/8" BS.