The usual method of hoisting the materials for a tall chimney in course of construction is to have outside the foot of the chimney a steam crab or winch, provided with a wire rope of sufficient length to reach to the top of the chimney and down again - about 100 ft. in length for a chimney 160 ft. high. In the base of the flue, a snatch-block is attached to a rail, or a rolled joist is built in. As the chimney is carried up, a couple of rolled steel joists are laid across the flue, on which is laid a plank floor, with a square opening in the centre for hoisting through, and three shear-legs with pulley-block are erected. The brickwork is carried up about 9 ft., and two other steel joists are laid across, the shear-legs being dismantled and refixed at the higher level, as is also the plank floor. When the next stage is reached, the first two joists are taken out and refixed at the higher level, and the shear-legs again moved, the operation being repeated every 9 ft. or so until the top of the chimney is reached.