thumb|upright=1.3|Two guy derricks at a granite quarry
A derrick is a lifting device composed at minimum of one guyed mast, as in a gin pole, which may be articulated over a load by adjusting its guys. Most derricks have at least two components, either a guyed mast or self-supporting tower, and a boom hinged at its base to provide articulation, as in a stiffleg derrick. The most basic type of derrick is controlled by three or four lines connected to the top of the mast, which allow it to both move laterally and cant up and down. To lift a load, a separate line runs up and over the mast with a hook on its free end, as with a crane.
Derricks are especially useful for high-rise rigging, jobs that cover a long period of time, or jobs when the impact to street or pedestrian traffic is a concern. Forms of derricks are commonly found aboard ships and at docking facilities. Large derricks mounted on dedicated vessels are known as floating derricks and shearlegs.
The term derrick is also applied to the framework supporting a drilling apparatus in an oil rig. The derrick derives its name from a type of gallows named after Thomas Derrick, an Elizabethan-era English executioner.
Types
There are various types of derrick based on how the tower or mast is set up and the use of boom.
Shearleg
A shearleg derrick is similar to a breast derrick with the exception that, instead of fixed guy wires that secure the top of the mast, it is secured by multiple reeved guys to permit handling loads at various radii by means of load tackle pulley system suspended from the mast top.