ANSI Grade 1 door locks offer the highest level of lock security. These locks are very difficult to pick or break and are resistant to any tampering with the lock's parts like removing pins, screws, etc.

The earliest patent for a double-acting pin tumbler lock was granted to American physician Abraham O. Stansbury in England in 1805, but the modern version, still in use today, was invented by American Linus Yale Sr. in 1848.

To make a new key for an existing lock, you cut a series of notches in the key so that it raises each of the upper pins just above the shear line. Essentially, you cut a pattern in the metal that matches the pattern of the pins in the lock.