Fig. 93
Under the continuous vibration of the scaffold they run down and release the chain considerably.
This can be prevented to some extent by inserting a piece of wood as shown on fig. [93], and tying its other end to a rigid member of the leg. In any case the chain requires frequent examination, and, if necessary, retightening.
Rollers.—Rollers ([fig. 94]) are used for moving heavy material along a smooth surface.
Fig. 94
Pegs should be fixed at their ends, as shown on [fig. 94], to form a handle by which they can be moved when under the material without danger to the workman’s hands, or better still, they should always be longer than the load is wide.
Levers.—Levers of ash, fitted with iron shoes, as [fig. 95], are used to prise heavy material off the ground, to facilitate removal on rollers or otherwise. In this case the lever acts as one of the first order. By connecting the weight to the rings A and B it can be used as a lever of the second or the third order.
Fig. 95