This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
After spending considerable time in cutting one mortise in a piece to make the settee described in a recent issue of Popular Mechanics Magazine, I devised the plan shown in the sketch which enabled me to cut all the mortises required in the time that I cut one in the ordinary manner. Two metal plates, one of which is shown in the sketch, having a perfectly straight edge, are clamped on the piece with the straight edge on the line of the mortise. A hacksaw is applied through holes bored at the ends and a cut sawed along against the metal edges. - Contributed" by George Gluck, Pittsburgh, Pennsylvania.