Firstly you will need to perform a search to display some search results. The CallSafe controls can be found on the toolbar next to the zoom buttons:

The CallSafe controls can also be found within Monitoring when a last call search is performed.

The two padlocks represent the two basic functions of the CallSafe feature, Lock Call and Unlock Call. When a call is locked, it is copied to a special CallSafe storage area. The call may be deleted from the recorder but the copy within the CallSafe area will remain.