A chain block or block and tackle is means of lifting heavy loads via sprocket driven chain that is reduced through a series of gears so that it may easier be driven by hand through another (non-load bearing) chain and sprocket.      Chain blocks are typically used in locations where there is no power available. Chain blocks are used for lifting light or heavy loads vertically where precision, and not speed, is a key requirement. They can be used safely and easily by just one person, like if a technician needs to lower a hoist into place carefully, or if a motor needs to be removed from a tight spot