Abstract: Support tube for a tubular assembly, particularly a vertical post for a railing, step of a ladder etc. at least one end of which is provided with an arcuate space into which a crossing tube can be fitted. At the arcuate edge of said arcuate space the wall of said support tube is bent into a protruding support extension (2). The support extension has been produced so that, prior to cutting the support tube to a desired length, a hole is drilled through its wall at the cutting line and the hole edges have been pulled out to form a collar protruding from the tube, whereafter the support tube is cut so that said collar is divided into extended support arches (2) which remain at the ends of separate support tubes.