A method of forming a joint (32) between two plastics extrusions (10) is disclosed which comprises mitring the extrusions (10) so that they form the desired angle to one another, removing part of the rear face of each extrusion (10) placing the mitred extrusions in a mould and injecting a resin material whereby to bond the extrusions (10) to one another and produce the desired joint (32) configuration. Because the front surface (24) of the joint in accordance with the invention is entirely made up from the original extrusion, there are no problems with raised sight-lines, colour differentials, surface differences, or colour matching. Moreover, the method of the invention allows a corner to be produced which has a clean right angled rather than radiused inner portion.