Fetters

Source Advanced Race Guide

Fetters are manacles fitted around the ankles rather than the wrists, and use the same rules for breaking, escape, and cost relative to size. A creature in fetters is entangled and can only move at half speed. In addition, a fettered creature must succeed at a DC 15 Acrobatics check to move more than its (reduced) speed in a round. If it fails the check by 5 or more, the creature falls prone.