A land drilling rig is a machine that creates holes in the earth subsurface and it can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells. There are two ways of rotation either using kelly that is the old technique or using the new technology that is top drive system where both will rotate the drill string to create drill the hole by the drilling bit. They can be mobile equipment mounted on trucks or trailers, or more permanent land. Small to medium-sized drilling rigs are mobile and used for drilling and work-over while larger rigs are capable of drilling through thousands of foot of the Earth's crust so they are used for deep drilling.