Shear line

The shear line, “línea de corte” in Spanish, is the boundary between the plug, the part that turns, and the housing, the fixed body of the cylinder. When no pin crosses it, the plug is free and turns with the key; if a single pin crosses it, the cylinder locks.

It is the basis of how almost all pin cylinders work: the correct key places the gap between key pin and driver pin at exactly that height in every chamber at the same time.

Almost all attacks that do not involve breaking revolve around it: picking, bumping or the comb pick all try, one way or another, to clear it without the key. That is why security pins are designed to catch precisely there.

It is not a part you can see or replace, but understanding the idea helps you choose. A quality cylinder, with tight tolerances and security pins, protects that line better. Ask about our security cylinders or our cylinder replacement service.