Another classic of magic, "sawing a woman in half" exists in literally thousands of variations, from simple bisections, to tri- and octa-sections, to self decapitations, to Penn and Teller's graphic and disturbing sawing a woman in half without putting her in a cabinet first. The saw itself may be of the lumberjack variety, something from a sawmill, razor-sharp steel plates, or even a nail file (for the delightful Sawing a BarbieTM in Half effect so popular at children's birthday parties). But no matter which variation is used, they all pretty much boil down to the same thing.
The magician and the magician's assistant present the audience with a large, horizontally oriented cabinet. The cabinet has a door that can be opened along its length, as well as holes through which an encabineted person's head and feet will show.
After the cabinet has been thoroughly displayed, the assistant climbs in, puts head and feet through the appropriate holes, and is locked inside. The magician then cuts the cabinet in half, accompanied by appropriate screams, etc., from the assistant. When the bisection is complete, the magician separates the halves of the cabinet to show that the assistant has truly been divided. The halves are then placed back together, the cabinet opened, and the assistant steps out no worse for wear, until raising hands triumphantly, the assistant reveals a costume has been cleanly cut across the middle, baring a horizontal incision across the waist which is apparently being held closed by nothing but a few sloppy stitches.
The easiest way to perform this effect is to use two assistants, each half the height of a more average assistant, with one standing on the others' shoulders and the resulting human tower draped in a single assistant's outfit. If such assistants are not available to you, you will have to rely on the alternative gimmick, described below.
The alternative gimmick is a far more expensive way to saw someone in half, but it will work with any assistant who has an modicum of flexibility. The gimmick consists of a pair of false legs, made up to look like the assistant's legs, within which are a pair of rods that act as stilts and have straps on top to securely hold the assistant's feet. Accompanying this is a false assistant's torso, similarly made up, but which has just barely enough room for the assistant to squat inside. When completely prepared, the assistant squats within the false torso, real arms and head showing, perched atop the stilts of the false legs. The effect, from a distance, is of a normal, unbisected assistant.
Once the gimmicked assistant is placed in the cabinet, the stilt's feet restraints are released. The "legs" can now be freely separated from the "torso," with the assistant remaining squished up in the latter when the box is separated. Once the box has been rejoined, the assistant puts feet back in the straps atop the stilts, and is ready to step out. After taking a carefully balanced bow (and releasing the Velcro "slit" in the "cut" costume) the assistant can walk off stage, remove the gimmicks, and have a secondary assistant administer a foot massage until feeling returns to the lower extremities.
We asked noted magician The Great Amazo why it is that we never see "Sawing a Man in Half." Amazo answered, "Who would want to saw a man in half?"