fitted a grooved socket cut obliquely in the other
beam. It is used in truss construction.

_No. 69. A bird's mouth joint_, Fig. 269, is an angular notch cut in a
timber to allow it to fit snugly over the member on which it rests. It
is used in rafters where they fit over the plate.

_No. 70. A plain or rubbed or squeezed or glue joint_, Fig. 269, is
one in which the edges of two boards are glued and rubbed together
tight. It is used in table-tops, drawing-boards, etc.

To make this joint, first the boards are all laid down flat, side by
side, and arranged in the proper order. Three considerations determine
what this order is to be: (1), if the grain is of prime importance, as
in quartered oak, then the boards are arranged so as to give the best
appearance of the grain. (2), if possible, the boards should be so
arranged that the warping of each board shall counteract that of the
adjacent ones. For this purpose the boards are so laid that the annual
rings of one shall alternate in direction with the annual rings of the
next, Fig. 280, a, p. 188. (3), if possible, the boards should be so
arranged that after being glued together they can all be planed smooth
in the same direction. When the above requirements have been met so
far as possible, this order should be marked on adjoining edges for
later identification. The edges of the boards to be joined should be
finished with a jointer.

There are two principal methods of gluing edge-to-edge joints, rubbing
and squeezing. In a rubbed joint, the surfaces to be joined should be
planed so as to meet thruout exactly. After properly planing one edge
of each board, keep one board in the vise, jointed edge up, and place
its to-be neighbor in position upon it. Then use these four tests for
an exact fit. (1) Sight down the end to see that the faces lie in the
same plane. (2) Examine the crack from both sides. Be sure that both
ends touch. Test this by pulling down hard on one end of the upper
board and noticing if the other end is still in contact. If the other
end opens, swing the upper board horizontally on the lower board to
see where the high place is and then correct it. (3) See if the upper
board stands firmly on the lower board by feeling gently to see if it
rocks, or by rapping lightly the lower board. (4) Slide the top board
slowly on the lower one to see if it adheres or "sucks."

[Illustration: Fig. 260. Applying Glue for an Edge-to-Edge Joint.]

After the pieces have