of 10 inches 26 mm although an elastomeric cord is shown the invention is not so limited and other types of spring members as previously discussed can also be used as will be well understood in the art the ends of the elastomeric cord 54 attach to means for releasably connecting to the edge surfaces 24 26 comprising hooks 56 the hooks 56 may be made from hard plastic having a hook opening of 1 u215c inches 35 mm the lower arm of the hooks 56 need be only u00bd inches 12 mm in length while the upper arm of the hooks 36 is typically 1 inch 25 mm in length the upper arm of the hooks 36 also includes an eyelet 56 a approximately u215c inches 10 mm in diameter the eyelets 36 a provide a means for connecting the ends of the elastomeric cord 54 to the j hooks 56 the ends of the elastomeric cord 54 are threaded respectively through the j hook eyelets 56 a and the outlet end portions 54 a of the cord are crimped respectively onto the input portions of the cord 54 using 3 16 inch c staple 58 again the invention is not limited to the above materials and dimensions and other materials and dimensions may be used as will be well understood in the art referring.