In the selection of hand-guided machines (i.e. drilling machines, circular handsaws) it should be considered for which activities and materials the machine is to be used, what degrees of accuracy have to be achieved, for how long the machine will run on a workday, what work position is to be adopted, what physical strength is required, etc. Ergonomic factors, such as the weight and dimensions of the machine, its surfaces and materials, the shape of handles and the type of grip, body posture and movements during work should also be taken into account. Prior to every use, machines must be checked for obvious defects: frequent defects are spelled casings and bare cables. Defective machines must immediately be removed from operation.