13. Various operations occur in the arts in which the assistance of an additional hand would be a great convenience to the workman, and in these cases tools or machines of the simplest structure come to our aid: vices of different forms, in which the material to be wrought is firmly grasped by screws, are of this kind, and are used in almost every workshop; but a more striking example may be found in the trade of the nail-maker.
Some kinds of nails, such as those used for defending the soles of coarse shoes, called hobnails, require a particular form of the head, which is made by the stroke of a die. The workman holds one end of the rod of iron out of which he forms the nails in his left hand; with his right hand he hammers the red-hot end of it into a point, and cutting the proper length almost off, bends it nearly at a right angle. He puts this into a hole in a small stake-iron immediately under a hammer which is connected with a treadle, and has a die sunk in its surface corresponding to the intended form of the head; and having given one part of the form to the head with the small hammer in his hand, he moves the treadle with his foot, disengages the other hammer, and completes the figure of the head; the returning stroke produced by the movement of the treadle striking the finished nail out of the hole in which it was retained. Without this substitution of his foot for another hand, the workman would, probably, be obliged to heat the nails twice over.