Definition of square set

A set of timbers used to provide support in a stope or an underground mine. Each timber set consists of a vertical post and two horizontal members known as a cap and girt. The timber ends are sawed to allow adjoining timbers to interlock. They are framed at mutual right angles, and when joined with other sets form a continuous timber framework that conforms to the irregular shape of the stope. The posts are 6 to 7 ft (1.83 to 2.13 m) high, while the caps and girts are 4 to 6 ft (1.22 to 1.83 m) long. Caps and girts are placed on top of the posts, a line of caps being at right angles to a line of girts. Square sets vary in dimensions at different mines, but in general should give a clear opening of at least 5 ft (1.52 m) each way between posts to afford sufficient working space in the stope, and a clear height of 6-1/2 ft (1.98 m) is about the minimum height desirable. This system of timber support can be adapted to large and irregular orebodies resulting in an elaborate network extending the full height and width of a stope.