It is often necessary to glue together narrow strips or boards to make one wide piece. This is not a very difficult operation if one has learned to control the plane properly. The first step is to select lumber suitable for such work and mark the sides which are to be the face of the finished piece. Also mark plainly the way of the grain, so that when the pieces are together they may all be planed from the same direction. (Fig. 120).

Examine the planes and be certain that they are sharp and not too much rounded, and that they will cut a shaving of good width but little thicker at the center than at the edges. The cutting edge should not be absolutely straight, neither should it be much curved.

Place one piece on edge in the vise and joint the edge carefully. Then lay it aside and joint the edge of the other piece which is to join the edge first jointed. It is not necessary to use a try-square on these edges. They should be at right angles to the surface of the piece, yet if they vary a little it does not matter so long as they make a level joint, and the pieces do not slip sidewise in the clamps. In making a glue joint a regular mechanic would never think of using a try-square. When you think you have the second edge correct, set the first piece on it and test with a straight edge, as shown in Fig. 120, to see if the pieces will make a true surface. Next examine the joint carefully from both sides and ends, as shown in Fig. 121. Continue to plane and test the joint in this manner until it gives a true surface and the edges come in perfect contact the entire length. Pressing down upon the corners will help to show defective ends. Also try rapping the under board. There should not be the slightest opening at the extreme ends even if the ends are to be cut off in finishing the piece. When the joint is correct there will be a peculiar sensation of suction, or adhesion, as you gently push or pull the top board on the under one. Do not attempt to glue the joint until it is correct as shown by each of these tests. Always put the pieces into the clamps to see if they are all right before applying any glue.

Probably the most common errors in making glue joints are to suppose that the joint does not require to be perfectly tight on the under or back side, and that dowels may be properly used in such joints. If you are to use cold glue for the joint, be careful to have it sufficiently thin to soak well into the joint before putting together. Also have plenty

of strong clamps. Allow the glue to become almost glazed before clamping the joint. Lay the clamps so that the joint will not be in wind, and use a sufficient number to expel every visible bit of glue as seen from the edge. The joint must be, in fact,

Fig. 120. Examining a Glue Joint with a Straight Edge.

wood to wood if it is to hold properly. Equal care must be taken with hot glue, but less clamping will

Fig. 121. Examining a Glue Joint.

suffice to expel the surplus glue. In using hot glue you must be certain that everything is ready for clamping before applying the glue. The clamps should all be in position and adjusted, so that the pieces may be put in place and the clamps tightened with the least possible loss of time. As hot glue will not hold if clamped too slowly, so cold glue will not hold if clamped too quickly. Considerable experience and judgment are required to get the best results with either. When properly used there is little if any difference in the holding power of the two kinds of glue. When the joint is poorly made the cold glue will hold better than the hot glue. With the inexperienced the additional time allowed in clamping the cold glue is quite an advantage. When much gluing is to be done, the hot glue is to be preferred because the piece may be taken from the clamps much sooner, thus saving a great deal of time and not requiring so many clamps. Care must be taken to keep the cold glue from becoming thick. The hot glue soon loses its strength by repeated heatings.