A stiffleg derrick, also known as a Scotch derrick, is a derrick with a boom similar to that of a guy derrick, but instead of using guy wires to secure the top of the mast, it uses two or more stiff members, called stifflegs, which are capable of resisting either tensile or compressive forces.OverviewA derrick is a composed at minimum of one, as in a, which may be articulated over a load by adjusting its. Most derricks have at least two components, either a guyed mast or self-supp. There are various types of derrick based on how the tower or mast is set up and the use of boom. An A-frame derrick is one in which the boom is hinged from a cross member between th. Another kind of derrick is used on and other drilled holes. Both the structure itself and the complex set of machines associated with it are referred to as a derrick. A derrick is also used on some offshore oil.