I was going to take photos, but they're actually quite boring; just black boxes with a hole at the front, a knob to move a bit of glass rod in front of the laser (to spread the beam vertically), and a switch at the back. Stick on laser warning signs and you have a reasonable facsimile of a laboratory laser that can also be used as a single-slit light box for about three pounds (if you ignore the cost of my labour). Even including it they're still a damned sight cheaper than purpose-built laboratory lasers, the cheapest I could find (which are more or less the same as the ones I just built but commercially made) cost eighty pounds apiece and don't do the ray box trick.
Incidentally, I thought that we'd come up with a new idea with the ray box thing, but it turns out that laser ray boxes (usually with five lasers) have been around for a while. They're ludicrously expensive, of course, but the fact that they exist will be half the battle if anyone says that we shouldn't be building such "dangerous" equipment. I may eventually try to build a five laser (or more likely three laser) box for teacher use, if I can get the beams parallel; they look pretty useful for demonstrations, and I ought to be able to knock them out for a pound a laser plus maybe 2-3 pounds for other components.
Next I must try to find some cheap diffraction gratings etc. to go with them...
