The stones were 'dressed' (worked on) and given mortice and tenon joints. 30 were erected as a 33 metres (108 ft) diameter circle of standing stones, with a ring of 30 lintel stones resting on top. The lintels were fitted to one another using another woodworking method, the tongue and groove joint. Each standing stone was about 4.1 metres (13 ft) high, 2.1 metres (6 ft 11 in) wide and weighed about 25 tons.