The disk lock is a special form of the padlock with some distinct advantages. The disk shape effectively combats the most common ways of forcing it open. The design with only a small opening in the shackle makes it very difficult to tamper with.

Disc locks are heavy-duty locks in the shape of a disc that are designed to make it nearly impossible for thieves to pick using shims or something similar. Not only are disc locks unbreakable by anything short of a power grinder, they're cheap too