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.
A very satisfactory adjustable holder for books or letters can be constructed of ordinary materials. A board is used for the base, and two pieces, C, cut from the grooved edges of flooring boards, are fastened on top as shown. A permanent end, A, is fastened to one end of the base. A good-size holder is 19 in. long, 6 in. wide, made of material 3/4in. thick.
The movable slide B has two pieces attached to its under side, which are cut from the tongued edges of flooring boards. The piece D answers the double purpose of a handle and brace. A lock, E, is made of a bolt, having a long thread and a square head. A hole is bored from the under side through the brace, and a portion of the wood is cut out to admit the nut. A square place is cut out to admit the square bolt head in the bottom pieces.
lock the slide, simply screw the nut upward so that it will push the bolt head against the base. - Contributed by James M. Kane, Doylestown, Pa.
Ill: The Holder may be Used for Books or Letters and Papers as a File