Frameworks and like structures

A framework comprising at least one frame member and wherein the framework extends in at least two dimensions, a linkage system associated with the framework and attached thereto at at least three non-collinear positions on the framework, said linkage system embodying two tension members, one of which extends from each of the two outer positions of said three non-collinear positions to the central position thereof where the tension members are each attached to one of two spaced points on a swivel member which is at least swivelable in the plane of the framework and is attached to the framework at the said central position by a connection with the swivel member being in tension between the connection and the points of attachment of the tension members and the connection being operable in use, to allow at least limited rotation about a point offset from the line of the tension members and thereby ensure that a change in tension in one of said tension members results in a rotation of the swivel member which causes a change in tension in the other tension member.