Rectangular Branch on a Round Pipe
A rectangular branch set square onto a round run, on its centre or offset: the run with its hole, and the branch folded at its corners. A rectangular branch set square onto a round run, on its centre or offset to one side: the run unrolled with the hole marked, and the branch in one plate folded at its corners with its saddle cut.
How the rectangular branch on a round pipe is developed, with a worked example · Intersections