Q. Why is it called a deadbolt lock?

Answer

Deadbolt locks are called so as they are one of the most secure locks that are not easy to open and without a key one cannot open it easily. Deadbolt locks in comparison to spring-loaded locks are very safe and secure as one cannot open them easily as in the case of spring-loaded. Also the spring-loaded locks and latches can be easily pushed manually but using a deadbolt is not easy to do so. Hence are called deadbolts i.e. they are immovable or dead.