2. _When possible, in laying out a joint, use the method of
superposition._ Fig. 302. By this is meant the method by which the
lay-out of one member is obtained directly from the other by laying
(superposing) the latter on the former and marking or scribing the
needed dimensions directly, instead of by measurement. It has the
advantages of simplicity, speed, and greater probability of fit.

[Illustration: Fig. 302. Marking by Superposition.]

Familiar illustrations are in the making of halved joints, Fig. 265,
Nos. 15-19, p. 178, dovetail joints, Fig. 267, Nos. 42-45, p. 180, and
scarfed or spliced joints, Fig. 264, Nos. 4-7, p. 177.

3. _Work systematically._ In case the same process is to be repeated
on a number of parts, complete this process in all before taking
up another process. This is the principle of the division of labor
applied to the individual workman.

In laying out duplicate or multiple parts, the proper cross
measurements should be carefully laid out on one piece and then
transferred with a try-square to the other parts laid accurately
beside it. So when a number of like pieces are to be gaged, all the
parts requiring the same setting should be gaged before the gage is
reset for another gaging. This is a great saving of time and insures
accuracy.

In making a number of like parts, if they are not too large much
of the work can often be done in one piece before it is cut up. For
example, to make a number of slats from a given piece of wood, the
piece may first be brought to such dimensions that the length will
be correct for the finished pieces and the thickness of the piece be
equal to the width of the slats, Fig. 303. The face may then be gaged
with a series of lines so that every other space will be equal to
the required thickness of each slat, and the alternate spaces be just
sufficient for the saw kerf and dressing. The slats may then be ripped
apart and dressed to size.

[Illustration: Fig. 303. Making a Number of Like Pieces from a Given
Piece.]

Or a long strip may be planed to thickness and width and then be
sawn up and finished to the proper lengths. For example, in a mitered
picture-frame it may be convenient to plane up two pieces, each one
long enough to make one long side and one short side.

In fitting up framed structures each part when fitted should be
distinctly marked, so that there may be no confusion in assembling.

4. _Where practicable secure the same conditions of gra