Instead of a separate bottom rounding tool being used for each different diameter of bolts or pins, a block having three or four gaps is often used, all the gaps being of different sizes, to suit various diameters of bolts and rods.

The making of such a block consists in either casting it of Bessemer steel or forging it of wrought iron ; sometimes adding a steel face for the gap part, in other cases making the block entirely of iron.

The forging is commenced by producing the square stem by drawing down one end of a bar or other component piece, and, when the stem is squared, a sufficient quantity of metal is allowed for the block, and the entire work cut from the bar or lump. The intended face side is next flattened or welded, if not solid, and the half-round gaps are formed with fullers. For this purpose, the places of the gaps are marked with a chisel, and the work is heated to nearly welding and put across a convenient opening to permit the square stem to hang between; or, if the steel is sufficiently reduced, it can be put into the square hole of an anvil. While thus situated, fullers of proper width are driven in at the marks, and with two or three heatings the gaps are roughly formed. The shaping of the gaps is next continued by hammering cold pieces of round iron or steel into the gaps, first at near welding heat, and afterwards at a dull red heat; each of the pieces used for shaping being of a proper diameter to form the opening desired. After all the shaping with fullers and pieces of round iron is completed, the burrs spread out at the angular extremities are filed off, and the smoothing of the gaps is effected with half-round or round files.

When the blocks are cast instead of being forged, the needful shaping and smoothing is effected with files only, because the gaps are cast nearly to the finished dimensions. Arounding-block is represented by Fig. 214.