Places hydraulic jacks, timbers, and posts in specified locations to form roof support system in underground mine: Examines hydraulic lines and tightens connections, using wrenches.
Helps place temporary posts or timbers under roof support beams when hydraulic jack failure occurs, or to supplement jacks in supporting roof. Advances coal conveyors and jack units forward to facilitate making new series of cuts in coal strata, using built-in or portable horizontal jacks.
