Abstract: A modular system uses a plurality of metal pipes each having an orthogonal array of coplanar openings at one end and a threaded bore at the other end. An insert is inserted in a first pipe bore at one end next to the openings, the insert having a set of like threaded bores aligned with the openings. A coupling member external the pipe is aligned with each opening and has a bore aligned with these openings. A plurality of bolts each with a threaded end is attached to a different threaded insert bore through a coupling member and pipe opening. The bolts each have an annular groove which is aligned with a threaded bore at a second pipe other end. A set screw in the second pipe threaded bore secures the bolt by engaging the groove, locking the second pipe to the first. A foot is threaded to a lowermost vertical pipe and an end cap is used as insert for the uppermost vertical pipe.