The classic arm chopper.
A proven winner, this arm chopper is popular with children and adults, too. The blade is shown to run the length of the Disecto frame. A volunteer inserts their arm into the large hole, underneath the blade. The magician inserts carrots into the smaller holes. Then a seeming impossibility takes place: The blade is pushed directly through the volunteer's arm. The carrots are cut, but the arm remains unharmed.
Plenty of opportunities for comedy and mystery are possible with this tried and tested trick. This is still a proven winner many years after its invention by Lester Lake.