How do you cut pipe ends for welding perpendicular joints?

DOWN AND DIRTY: For an end or corner joint, cut each intercepting piece at a 45. For T joints, cut the top of the post with two opposing 22.5s to give you a full 45 and cut your top rail with a corresponding 45 to the longitudinal centerline. Peen pieces into place if necessary.

Saddle markers are available at most oilfield supply or welding supply stores. They are available for all common pipe sizes... Simply clamp it on the pipe and mark your cut. No peening necessary.