The ordinary carpenter’s square — the right tool: it is easy to check or to mark the connection of the parts at right angles. However, he will be able to in addition to these functions and even measure the length of the parts, if you supply it with the proper scale. To do this, regardless of it metal or wood, it is easiest with the student line, gluing it on the long side of the polygon.
V. GOLOVASHIN, Rybnoe, Ryazan region.