I made one after reading about dry fire bows somewhere. I used a piece of 3/4" schedule 40 pvc, and 1/8" braided poly rope for the string.
1.)I cut the "bow" 60" long
2.)drill holes 1" down from each end of the pipe
3.)run the rope through the holes and a washer on the other side (I used rubber washers)
4.)tie one end of the rope in a knot, pull the other end to desired brace height (this works much better with 2 people) and tie that end off
Now you have yourself a "dry fire" bow that I use to teach myself proper form. I shoot it a occasionally throughout the day, usually 5 shots or so every time I walk past it. One note, keep the brace height high as it will bite your forearm. I have mine set at 10.5" and still like to have longsleeves or an arm guard on...Mike