This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Timber comes from the mills rough from the saw, and before it can be used for any finished work it must be prepared to receive paint or other kinds of finish. This preparation consists in a smoothing or planing which can be carried to any extent, including sandpapering or even polishing. The instruments used for the rougher part of this work are called planes, after which, if more smoothing is required, come scrapers and sandpaper. There are a great many different kinds of planes, but the principle of all of them is the same. They consist of a sharp blade, or knife, in the form of a chisel, which is held in a large block of wood or iron by means of clamps, so that the knife can be kept steady and guided easily. The knife projects at the bottom of the back through a slot, and takes off a shaving which is larger or smaller according to the projection of the knife. For smoothing, the cutting edge of the knife must be absolutely straight and must be clamped into the block in such a way that the projection will be exactly the same all along the edge. Any imperfections in the edge of the knife will be repeated on the surface of the wood. Planes are in general of two kinds, namely, "jack planes" and "trying planes."