Different designations are possible: drill protection
One of the common methods of overcoming lock cylinders is drilling. To defend against drilling attempts with HSS (high-speed steel) drills, hardened pins, bolts, steel balls, sintered material and carbide inserts are very often inserted into the rotor in the front area of the key entry.
In the cylinder itself, sintered plates, steel rollers or similar difficult-to-machine steels and materials are used for this purpose.
These are arranged in such a way that when drilling is attempted, the drill bit breaks or is deflected in such a way that the cam (also known as the locking cam) cannot be reached and can be rotated using auxiliary means.