Abstract: A door or window assembly comprising a rigid first frame (1) defining an opening, and a second frame (9) adapted to be fitted into and close off the opening in the first frame (1), the first frame (1) being at least partly or wholly hollow and having a surface part with an opening (4) leading into a channel section (2) partly defined by side walls (6) of the said first frame (1), the second frame (9) including retaining means (12) of which a part can enter said channel section (2) through said opening (4) and thereafter securely engage the first frame (1) to prevent the second frame (9) from being withdrawn from the first frame (1).

Abstract: A window assembly comprises a rigid first frame (1) defining an opening; and a glazed second frame (9) adapted to be fitted into and close off the opening in the first frame (1), the second frame (9) being of a plastics material and having a resilient part (27) integral therewith which permits the second frame (9) to be moved in one direction into the opening and thereafter coacts with the first frame (1) to prevent the second frame (9) from being withdrawn from the first frame (1) in the direction which is opposite to the first direction.