This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol6", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Two of these tools at least are necessary for the proper laying of floor-boards. The tool itself (Fig. 216) is a kind of elongated vice, having one jaw roughly adjustable to length by means of a pin passed through any of the holes in the main bar, on which it slides freely, and the other jaw operated by means of a screw and handle as shown. Its use consists in holding the floor-boards firmly edge to edge during the operation of nailing them to the joists, thus avoiding the possibility of any interstices occurring between them.
The floor cramp is generally made throughout of wrought steel.
The Stone Cramp (Fig. 217) is an appliance for lifting light pieces of dressed stone. The cramp, which is made throughout of steel, is first screwed tightly down on to the piece of stone to be lifted, care being taken to insert a small flat piece of wood packing on each side, between the steel jaws of the cramp and the face of the stone, to prevent damage to the finished surface. The sliding attachment on the back of the cramp is then moved along until it is in such a position that, when the stone is lifted by the ring let into this attachment, it will hang level. The lower hook of a pair of blocks can then be placed in the ring and the stone raised easily into position.