The clamp (1) has two L-shaped grips (2,3) which have interlocking profiles and which are also linked by two sloping thrust faces (8). A threaded fastener (4) is located through a slot (14) in one section and is threaded into a tapped hole in the other section. As the threaded fastener pulls the two sections together they slide on the sloping thrust faces until their outer edge (9) grip the square profile. On of the clamp sections has another tapped hole (16) to take a securing screw (6) which fastens a scaffold clamp, to enable square section tubing to be clamped to round scaffold tubing.
