Wrest planks of pianos should be built up of three sections - a beech centre, a maple or sycamore facing i in. or 3/8 in. thick, and a pine backing. If the facing alone is split, it is only necessary to replace that portion; but if the plank is so split that a new one must be inserted, proceed as follows. First remove all the wires. If the covered ones can be used again, thread them on a piece of wire in the order in which they were taken off. Remove the wrest-pins, and with a stout piece of brown paper and heelball make a clean imprint of the holes, bridge, etc. Carefully remove the bridge screws or bolts; the old plank may then be chopped out with a mallet and stout chisel. The prepared plank should be cut to exact length and secured in position with good hot glue, and screwed up tightly for several days with iron cramps having deep jaws. When these are removed, clean up the face for the bridge and holes for wrest-pins, their exact positions being determined by means of the brown paper, which is laid in position, and secured while a sharp tap is given with a hammer and centre punch where the holes should be bored. The bridge should be fastened with hot thin glue and brass pins and the necessary bolts, screws, or dowels, and a piece of mahogany or birch capping laid on.

But if the instrument is fitted with a half lid it should have a final cleaning up, and several coats of white hard spirit varnish should be applied before the wrest-pins are inserted.