You take the bottom and cut it out into a comb or combs.
They work and really make your hair look good, from my own experience.
And they don't hurt.. but if they do for oyu, you might wanna cut down the "sharp" edges.
I guess you can make it out of many other things, as well.
Are they pretty? No :)
But that's not the point. This is for the poor people.. and anyone else who would like to try it out.
You can make it out of any similar object, really.