The neatest way in small boxes is from the end, or better still it may be only glued.
_No.25.A dado or grooved joint_, Fig.

266, is made by cutting in one member a groove into which the end or edge of the other member fits.
Properly speaking a groove runs with the grain, a dado across it, so that the bottom of a drawer is inserted in a groove while the back of the drawer is inserted in a dado.

Where the whole of the end of one member is let into the other, such a dado is also called a housed dado.

Treads of stairs are housed into string boards.
To lay out a dado joint: After carefully dressing up both pieces to be joined, locate accurately with a knife point, on the member to be dadoed, called X, one side of the dado, and square across the piece with a try-square and knife.

Then locate the other side of the dado by placing, if possible, the proper part of the other member, called Y, close to the line drawn.