Concealed joint structure

A concealed joint structure - for respective pairs of mitre-corner jointed, extruded aluminium, head and sill channel frame members to be horizontally-fixed within shower enclosure as sliding door supports - has a respective plastic internal connector in the form of a profiled plastic corner stake which has a groove formed on its external corner to match a correspondingly profiled rib projecting from the inside corner of an angled decorative plastic cover which has two flat walls mutually arranged at right angles and is formed with a profiled rib which extends from and axially along the inner corner of the cover; all forms of the cover can be slid directly onto the external corner of corner stake connector after it has mitre-corner jointed the pair of channel frame members of the shower enclosure to conceal the joint, thus protecting against any exposed jagged cut edges of the connected channel frame members and providing a decorative finish after installation of the assembled structure and sliding shower doors into a shower enclosure. 18, 22 221FIG. 1 22a 22)b 23a 23b 22a