Abstract: An auxiliary locking device to be employed in a door knob includes a lock body that has at least two parallel through-bores extending through the body. A first retaining bolt is slidably received in one of the through-bores and includes two ends extending out from the lock body. A second retaining bolt is slidably received in the other one of the through bore and has an end portion extending from the lock body. The end portion of the second bolt has a plate member with an opening around the periphery of which a wall body is mounted. The wall body confines a through-hole that generally has a cross-section equal to and in communication with the opening.