using a pulley system connected to the top of the tower. Breast A breast derrick is a derrick without a boom with a mast constructed from two upright members. The upright members are more spread at their bottom ends than their top ends. There are crossbars to join the two members from the bottom to the top to form a mast.. Chicago boom A Chicago boom derrick is a derrick with a boom which is attached to an external structure. The external upright member of the structure serves as the mast, and the boom is stepped in a fixed socket clamped to the upright. The boom is connected to at least three pulley systems to control the position of the boom. For example, a pulley system is connected to the top of the boom and the higher area of the external structure and two pulley systems near the top of the boom connected on either side of the boom to the external structure. The position of the top of the boom can be controlled by manipulating these pulley systems. The load is lifted from a separate pulley system that is connected to the top of the boom. Gin pole Gin pole derrick (also known as standing derrick or pole derrick) is a derrick without a boom with single tower or mast supported by 4 guy wires (two side guys, fore guy and rear guy). Its guys are so arranged from its top as to permit leaning the mast in any direction. The base of the tower is hinged and the top of the tower is connected to a pulley system for load lifting. As this is a simple derrick system, it is considered to be used by some agencies as an improvised rescue derrick in an emergency situation where no suitable rescue derrick or crane is available. Guy Guy derrick (also known as boom derrick) is a fixed guyed mast derrick that can be rotated and connected to a boom. The mast is in upright position with the base that can make the mast rotate, but not to be lean in any direction. The top of the mast is connected to many guy wires which are anchored to the ground to support the load. At the base, the mast is also connect to the bottom end of the boom. The boom extends outward and upward to the desired position. The