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 paper trimmer and mat cutter can be made from a wafer razor blade. As a paper trimmer, place the blade C over the part A of the razor, as shown, with only two of the holes engaging in one post and the center screw. Then place the part B i n position and clamp with the handle. This will allow about 1/2 in. of the blade to project at one end. If a part of the extending blade is cut or broken off, it will be more easily handled. The cutter is guided along the straightedge as shown in Fig. 1.
If it is desired to make a more permanent form of instrument, or if no holder is at hand and only a castoff wafer blade, a handle, C, may be cut from a piece of wood and fitted with two or three binding-posts, A, taken from an old battery, to hold the blade B in place, as shown in Fig. 2.
Ill: Blade Attached to Handle