The durability of a lockset or deadbolt is determined by how well it can withstand an excessive amount of weight in addition to repeated, long-term usage.
There are two different kinds of tests that a lockset or deadbolt must go through to determine how durable it is: operation tests and cycling tests.
Operation tests measure how much torque (twisting) and pressure a lockset can stand while still operating normally. In other words, operation tests measure how easily you can open your door even when there’s an unwanted amount of weight on the handle—like a hanging purse or a coat.
The cycling test, on the other hand, makes sure your lock or deadbolt can withstand repeated, long-term usage. Products with an ‘A’ rating in Durability are subjected to 400,000 cycles of unlatching, opening, closing and re-latching. This translates to 100 years of use assuming using the locks 10 times per day and is an example of the rigorous testing BHMA certified products must withstand.