DIY science toys for kids

Amara sez, "Using a CD to demonstrate light spectra is a simple way to show to anyone the basic principles of light. I learned of that trick from my colleague, but here in this web site we have a collection of toys like the CD trick to make at home to demonstrate simple science principles. Science principles that might seem at first, too complicated to understand, but in fact, are simple enough for kids."
Our spectroscope has three main parts. There is a slit made from two razor blades, a diffraction grating made from a CD disk, and a viewing port, made from a paper tube.

To make sure that all three parts are lined up properly, we will use the CD disk as a measuring device, and mark the spots where the slit and the viewing port will go.

Set the CD disk on top of the box, about a half inch from the left edge, and close to the box's bottom, as shown in the photo. Use a pen to trace the circle inside the CD disk onto the box. This mark shows us where the paper tube will go.

Link (Thanks, Amara!)