Jam nuts are thin hex nuts usually used as a second nut that is "jammed" (tightened) against a full size nut or alone as a thin nut. They are used to "lock" turnbuckles and control linkages, like steering tie rods, after adjustment. Hex is short for hexagon, which means they have six sides. Jam nuts are also known as: half height nuts, hex thin nuts (even though they are referred to as half height, they are really two-thirds height). Jam nuts are used without lock washers when jammed against another nut, and may be used with lock washers when installed as a single nut.