For single-slit diffraction and double-slit interference experiments, commercially made slits can be the most expensive parts, especially since the prices of laser pointers have become very low. One option is to use a razor blade to cut slits in either paint or electrical tape on microscope slides. However, this takes practice, and there is some risk of injury, so it may not be reasonable to expect students to make their own slits in this way. Also, measuring the width and the separation of the slits produced requires a microscope. A simple, inexpensive alternative is to use the gaps of a fine-toothed comb as slits.