A clamp (10) for holding two elongate members (23a, 23b), so that they extend at a preset angle from each other, comprises two clamp portions (12, 14) each having co-operating engaging surfaces (16a, 16b), each clamp portion having a co-axial bore (18a, 18b) extending perpendicularly to the engaging surfaces and a receiving portion for holding one of the elongate members; a stem or rod (19), passing through the bore of the clamp portions and attached at one end to a lever or handle (20) for rotating the stem in the bore, and a cam acting between the stem and at least one of the clamp portions so that the clamp portions can be moved from a position in which the engaging surfaces are not engaged to a position in which the engaging surfaces co-operatively engage by rotating the lever by approximately 90°. This clamp is quick to operate and allows umbrella shafts and poles to be assembled in a versatile way. In particular such clamps can be used to form an umbrella assembly (40) comprising an umbrella head and a pole (42) for supporting the umbrella head, the umbrella head having a runner slidably mounted on a shaft portion of the umbrella head and stretchers extending radially from the said runner to the ribs, and clamps (10, 10', 10") for releasably attaching the umbrella head to the pole and various poles together in a frame. |