Abstract: A joint between a member having an inwardly lipped, channel-shaped cross section and a hollow rail comprises a connection including a key portion which has a head with inclined engagement surfaces located between the sides of the channel-shaped member which also includes engagement surfaces having a corresponding inclination, a clamping device engaging means on the connector to urge the engagement surfaces of the head of the key portion into locking engagement with the surfaces on the lips so that the lips are prevented from splaying apart when the joint is stressed, the connector also including a tongue portion extending away from the key portion and having a threaded hole at the base of a ramp surface, the tongue being inserted into the hollow rail.