In mitre joints the shrinkage of the boards in width, as dotted, does not open the external angle of the joint, though the inner angle does open slightly, as shown by the dotted lines in Fig. 145.

Butt Joints 200125

Fig. 145.

Butt Joints 200126

Fig. 146.

Butt Joints 200127

Fig. 147.

Butt Joints 200128

Fig. 148.

Butt Joints 200129

Fig. 149.

When, however, one piece is butted against the other, the piece that has its grain parallel to the plane of the joint is drawn away from the other as it contracts, leaving an opening at 0 (Fig. 146).

To hide this opening by its shadow a bead is often " stuck" on to the piece, as shown at b, Fig. 147.

Or in angles exposed to injury, such as those of chimney breasts, passages, etc., a bead is formed so as to avoid the sharp arris (Fig. 148).

This forms what is called a staff bead.

Interior angles, such as those of dados or skirtings, may be formed with a simple joint as in Fig. 148. In this case the opening caused by shrinkage is not visible (except on the top edge, which is generally mitred as far down as the depth of the moulding), as it is covered by the wall.

The above joints, slightly modified, are all applicable to acute and obtuse, as well as to right angles.

A common joint for uniting the angles of cisterns or troughs is shown m Fig. 150.

When the angles on both sides are seen, one piece may be housed into the other, as in Fig. 151.

If the end, x, cannot be left on, the tongue must be made smaller as in Fig. 149, so that sufficient wood may be left on the outside for strength.

Butt Joints 200130

Fig. 150.

Butt Joints 200131

Fig. 151.