Connection members for constructional system

A constructional system for making joints between separate lengths which may be extruded which comprises a first length having an outwardly facing, open ended, undercut channel formation with a mouth along one face thereof, a second length having two such channels with mouths along one face thereof, a connection member having a base which is passable into an end of the channel formation along said one face of said first length and is of such form as to be prevented thereby from passing said channel mouth while movable to any desired position along the channel, securing means accessible for actuation through said mouth of said channel in said first length whereby the connection member may be secured by its base to said first length at said desired position therealong to project through said mouth of said channel in said first length, said connection member having a spaced pair of side members each extending along a respective one of a pair of parallel axes and passable in its axial direction into the end of a respective one of the two channel formations along the said one face of said second length, each of said side members having a tapped hole therethrough inclined to the axis thereof in the direction of the base thereof, and a threaded member screwed into each such hole and accessible for actuation through said mouth of the associated channel in said second length whereby tightening of the threaded members draws the second length into rigid fixed relationship with said first length.