An attachment system for attaching a flexible enclosure to a boat windshield frame includes a frame trim piece with a longitudinally and transversely extending groove retaining a resilient insert. The insert has a pair of legs extending from one end of a shank and touching to conceal the groove. A screw snap stud can be inserted at any selected position along the groove to self-tap into the walls of the groove and releasably retain a cooperating fastener on the flexible enclosure. If the stud is removed, the insert legs return to the original position. Alternatively, the insert is not used or the insert does not include the legs.