Medium Split Lock washers are a hardened split curcular washer with a slightly tapezoidal wire section. Split Lock washers apply greater bolt tension per unit of applied torque as well as a hardened bearing surface adding to a more uniform torque control. These lock washers resist loosening caused by vibration and corrosion. These lock washers are the preferred style of lock washer for applications with a hardened bearing surface. Lock washers work by applying a spring force against the nut or bolt head.