Abstract: A panel joining device formed in the manner of an extrusion which in section takes the form of two intersecting planes where the longitudinal one edge of each plane includes a vertically projecting first ridge. A second ridge is formed on the opposite face of each plane, across the intersection, such that the first ridge of one plane is directed towards the second ridge projection of the second plane. The first and second ridges are furthermore disposed to engage a first and second groove respectively formed on the face and in the edge surface of a panel to be joined with a similarly grooved other panel by the joining device.