So to compliment the small light brake I uploaded earlier here is a welded brake that will handle 20 gauge sheet metal up to 36" wide, thicker gauges in shorter widths. It is less complicated than many I have seen without giving up usefulness. An inexpensive stick welder and a method of cutting your stock to size, a drill and grinder are the main tools you will require. Even an inexpensive import in this size goes for $400 +.
This plan came from The Lincoln Foundations book "Arc Welded Projects Volume III" there are more good plans in this volume, heres the cover and brake plan.