Question

what is interlocking

Answer 1

used to prevent undesired states in a finite-state machine, and may consist of any electrical, electronic, or mechanical devices or systems. In most applications, an interlock is used to help prevent a machine from harming its operator or damaging itself by preventing one element from changing state due to the state of another element, and vice versa. Elevators are equipped with an interlock that prevents the moving elevator from opening its doors, and prevents the stationary elevator (with open doors) from moving. Although both are idiot proof strategies, an interlock should not be confused with a simple safety switch

Answer 2

Engage with each other by overlapping or by the fitting together of projections and recesses