of an ore deposit from the top downwards. Like shrinkage stoping, underhand stoping is most suitable for steeply dipping ore bodies. Because of the mechanical advantage it offers hand tools being struck downward (rather than upward, against gravity), this method was dominant prior to the invention of rock blasting and powered tools. Overhand stoping In overhand stoping, the deposit is worked from the bottom upward, the reverse of underhand stoping. With the advent of rock blasting and power drills, it became the predominant direction of stoping. Combined stoping In combined stoping, the deposit is simultaneously worked from the bottom upward and the top downward, combining the techniques of overhand and underhand stoping into a single approach. Breast stoping Breast stoping is a method used in horizontal or near-horizontal ore bodies, where gravity is not usable to move the ore around. Breast stoping lacks the characteristic "steps" of either underhand or overhand stoping, being mined in a singular cut. Room and pillar is a type of breast stoping. Timbered-stope systems Stull stoping Stull stoping is a form of stoping used in hardrock mining that uses systematic or random timbering ("stulls") placed between the foot and hanging wall of the vein. The method requires that the hanging wall and often the footwall be of competent rock as the stulls provide the only artificial support. This type of stope has been used up to a depth of 3,500 feet (1,077 m) and at intervals up to 12 feet (3.7 m) wide. The 1893 mining disaster at Dolcoath mine in Cornwall was caused by failure of the stulls holding up a huge weight of waste rock. Square-set stoping Square set was invented in the Comstock Lode, Virginia City, Nevada in the 1860s. square-set timbering. Square-set stoping is a historical method stoping which relies on interlocking timbers set into place forming a grid, wedged tightly against the rock. As the mining progresses, generally upwards, new timber sets are added to fill the void. Ore is dropped through the sets freely or fed into chutes and either loaded into ore cars or mucked out from there. Depending on rock conditions and other technical considerations, once the stope has reached its engineered height, it may be left open or backfilled for support. A common historical method of hydraulic fill involved dumping waste rock into a completed stope, then slurrying in a mixture of mill sand and water.