Abstract: Two weatherstrippings are joined before the application of any backing to the woven strip of artificial yarn which carries the rows of pile which form the air barrier. A plastics material is placed across the butted ends of the strips in contact with the lower surfaces of the strips and the two are then welded together ultrasonically to join the weatherstrippings. The backing can then be applied over the joint. A jig for performing such a joining method comprises two holders for carrying the strips by their pile with the lower surfaces uppermost. The holders are formed in two parts to allow the strips to be cut to form a clean straight end. One part of each holder is then removed and the remaining parts slid together to butt the two strips. A piece of heat-weldable material is then placed over the butted ends in contact with the lower surfaces and is heat welded to the strips to complete the join.