There are various ways to unlock a door without a key. You can pick the lock with lock picks,
Master key: The master key can open all locks you have in your residential or commercial property.
Keypad Locks
They can be battery-powered or mechanical and generally utilize deadbolt locks, knob locks or mortise locks for the actual locking mechanism. These door locks offer enhanced versatility and enable entry without a key, although many also contain keyholes for alternate unlocking mechanisms.
For pin tumbler locks, including deadbolts and entry doors, make a pick set out of 2 bobby pins or paper clips. Stick them into the lock and wiggle them until the lock opens. Use an unbent paper clip or a hairpin for locks on privacy door knobs.
A three digit lock can have its key value between range "000" - "999". So basically 1000 combinations have to be tried to open the lock. So I had to generate the shortest string such that all possible combinations (i.e between "000"-"999") would be checked.
You can use paperclips as picks in a pinch, and a tension wrench can be any tool used to create tension, including a flathead screwdriver. One of the most common (and easiest to pick) locks is the pin-and-tumbler, which is a type of cylinder lock.
Lock Picking
It can be a very fiddly practise which can be risky for an intruder as the longer it takes, the bigger risk that they might get caught. Essentially, every lock that has key cylinder is susceptible to lock picking.
Knob locks are the most common type of door lock installed on the internal doors. Knob locks are not ideal for external use due to their limited amount of security. But these locks can be installed on exterior doors to provide extra security when used with deadbolt locks.