In lock picking a cylinder lock, the shear line, also known as the split line in Australia, is where the inner cylinder ends and the outer cylinder begins. When a correct change key or master key is inserted in the cylinder, it will align the pin segments with the shearline and allow the cylinder to be turned. This break in the lock mechanism is a vital part of the lockpicking process, as it allows a picked pin to "hang" while the others are being picked.

Locksmithing