This is a tutorial on how to make a doorway pull-up bar that does not require holes in any door frames or walls to mount it; which makes it perfect for college dorms or other temporary living quarters. It pushes against the door at two different points when weight is applied to safely wedge itself into the frame without the use of screws or bolts. It has an estimated maximum capacity load of 300 lbs. It allows for wide, regular, close, and hammer-grip pull-ups and chin-ups. Some of the work for this instructable are inspired by Shenandoah of http://www.angelfire.com/ny5/shenandoah/Grunt/Bodyweight.html
and other commercial products on the market.