A mitred corner of a frame has a clamp 1 clamping together a top member 2 and a side member 3. The corner is at a corner of a glass panel 4 accommodated within a frame made up of four such members, each clamped together by similar clamps. The frame members are mitred at 45° with faces 8. Webs 7 of the frame members are drilled with bores 9 fixing screws 10 The screws engage in two clamp elements are used at each corner, in the form of stainless steel blocks 12,13. The block 12 has at its end close to the mitre faces 8, a 45° surface 17 and a threaded end bore 19 is provided. The block 13 has a finger 24 extending past the face 8. The finger has a clearance screw bore 25 and at its distal end a snib 26 directed towards the block 12.