Abstract: A form of scaffolding construction is described in which rectangular frame units extend between and are screwed to vertical scaffloding tubes. Clamping devices for this purpose comprise a rigid angle element having a short arm and a longer arm, a short element hinged to the longer arm, a longer element hinged to the short element and having at its free end means whereby it can be releasably interlocked to the shorter arm of the angle element. The tubes are disposed side by side within the device and are separated by a dividing element connected to the longer arm. A clamping screw extending through the short element is tightened to interlock the longer element to the shorter arm of the angle element about the two tubes.