Backs

1. The height of ore available above a given working level. If the orebody has been proved by shaft sinking to a depth of 300 ft (91 m) from the surface, the orebody is said to have 300 ft (91 m) of backs. See also: back
2. A quarryman's term for one set of joints traversing the rock, the other set being known as cutters. Nelson
3. A system of joints in coal or stratified mineral oblique to the bedding at an angle of 35 degrees to 75 degrees . See also: slips BS, 11
4. Slips; used to denote a slip met with first at floor level. Syn: hugger

Source: Dictionary of Mining, Mineral, and Related Terms