High Security Abloy PRO 300 Deadbolt Lock with Knob - Includes 5 Keys & Keycode Card (30/40 Knob Size) - Ideal for Homes, Offices & Commercial Properties

Thumbturn function: The cylinder with a thumbturn knob and a safety catch is locked and unlocked just like any other lock of such type. The feature that adds an extra function is the securing bolt. TPulling the thumbturn knob until the securing bolt springs out from the slot in the thumbturn knob puts out of operation the part of the locking mechanism that is controlled by a key, which makes unlocking the door with a key impossible from outside. In order to restore the key function, it is necessary to position the thumbturn knob vertically so that the securing bolt is pointed upwards and then push the bolt into the knob. The function is particularly useful against unwanted opening from the outside.