178, the gaging is all done from what will be one of the flush surfaces of the joined pieces.

Then, if the gaged line should be slightly more or less than half the thickness of the pieces the closeness of the joint would not be affected.
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.