The rack is a torture device consisting of a rectangular, usually wooden frame, slightly raised from the ground, with a roller at one or both ends. The victim's ankles are fastened to one roller and the wrists are chained to the other. As the interrogation progresses, a handle and ratchet mechanism attached to the top roller are used to very gradually retract the chains, slowly increasing the strain on the prisoner's shoulders, hips, knees, and elbows and causing excruciating pain. By means of pulleys and levers, this roller could be rotated on its own axis, thus straining the ropes until the sufferer's joints were dislocated and eventually separated. Additionally, if muscle fibres are stretched excessively, they lose their ability to contract, rendering them ineffective.