surface of the elongated cylinder 41 has helical ridges 42 protruding from the surface thereof and extending substantially the length thereof to increase the friction between the elongated cylinder 41 and the fabric these ridges 42 may consist of velcro strips cemented to the surface of the elongated cylinder 41 to increase friction between the pressure applying member 40 and the fabric means for resiliently biasing the pressure applying member 40 comprises a pair of eyelets 40 a that are attached respectively to each end of the cylinder 41 at the longitudinal axis of thereof the eyelets 40 a are preferably countersunk into the cylinder 41 for added strength the tensioning means for resiliently biasing the pressure applying member 40 also preferably comprises a pair of expansion spring members 44 attached respectively to the eyelets 40 a at the ends of the cylinder 41 the expansion springs 44 may be u00bc inches in diameter 6 mm with a length of 2 inches 50 mm the other end of the expansion springs 44 attach respectively to means for releasably connecting to edge surfaces 24 26 comprising hooks 46 which may be s hooks or any other type of suitable hook such as j hooks the hooks 46 are preferably made from stainless steel and may have a large hook opening of 1 u215c inches 35 mm the lower arm of the hooks 46 need be only u00bd inches 12 mm in length while the upper arm of the s hooks 46 is typically 1 inch 25 mm in length the.