Dogs notice that when his owner goes to get the mail or do the laundry, only one lock engages.

There was a quiet whine as the lock engaged.

When he slammed the door after grabbing the gun, the lock had automatically engaged.

There was a satisfying click as the lock engaged.

He delays so long that the electric lock engages once more.

"Please," he panted, pushing down hard on the door until he heard the lock engage.

With one hand he fumbled down, engaged the lock.

The heavy door shut behind him, the locks engaging.

When Kirk heard the lock engage, he applied the finishing touch.

As the magnetic locks engaged, Worf opened his diplomatic pouch and reached inside.