The CMI Rope Jack is a Mechanical Advantage tool for pre-tensioning static lines, light lifting and cabling. Small and light enough to be carried aloft by a climber for Mechanical Advantage win the crown. The length of the handle on the Rope Jack limits excessive loading to avoid rope damage. Under no circumstances should a cheater bar be used to increase leverage as it may damage the unit, the rope, or severely injure personnel. lt is designed to be used by only one individual using one hand only. lt shall be removed before any 'shock' load is applied; lt shall NOT be used for heavy or dynamic loads as there are other tools available for those applications. It can attach mid-line and can run virtually any length of rope. The CMI Rope Jack is used to remove slack and stretch for lowering and to lift the tips on light limbs without having to break out the big guns. It is NOT for heavy loads! The Rope Jack is approved for life support use as long as another form of progress capture device is used in conjunction w the device. Never use the Rope Jack by itself for hauling human cargo. The CMI Rope Jack is approved for static ropes s 3/8 5/8 inch diameters.