The jack plane or the jointer should be used in edge planing.

Both of these planes have their blades sharpened slightly crowning. (Figs. 19 and 21.)

The jointer, which is about 24" long, should be used when making glue joints or edges that must be very straight. It may be used to do the whole job, or it may be kept extra sharp and finely adjusted and used only to take the last few shavings.

See that each plane is adjusted so that the center of the blade projects slightly while the edges are still even with or slightly above the sole of the plane.

Test the edge of the board with the try-square, holding the beam against the working face and the blade across the edge. (See Fig. 24.)

With the center of the plane over the high side, take a shaving, keeping the sole of the plane firmly pressed against the edge of the board.

Fig. 25 shows what takes place. Since the center of the plane iron projects farther than the edges, the shaving taken is thicker on one edge than the other, and each shaving taken with the plane held in this position brings the edge nearer square with the face than before. A few such shavings will bring the edge of the board square with its working face.

5. The first edge planed is called the joint edge. It is always given a witness mark by which it may be distinguished.