Heavy-duty locks are a type of security device that is designed to provide maximum protection against forced entry. They are typically made from hardened steel and feature multiple locking mechanisms, such as deadbolts, keyed cylinders, and combination locks. The term 'heavy-duty locks' is often used to refer to locks that are designed to withstand extreme force or tampering. MOP is an acronym for Master Open Profile, which is a type of lock cylinder that is designed to be more secure than traditional cylinders.