The removal of timbers and supports from abandoned or worked out mine areas. This work is highly specialized and should be attempted only by the most experienced persons. Generally, timbers are pulled by a timber puller that permits the operator to be under a safe roof while doing this work. In some cases, where so much weight is resting 983 on the timber that it cannot be removed safely, it must be shot out by use of explosives, and the roof allowed to fall.