Abstract: A fabric tube has a closed bottom and an open top. The closed bottom forms a semicircular section when unstretched. The tube has a cylindrical section between the open top and the semicircular section. The cylindrical section has a common circumference when unstretched. A tunnel is formed in the open top of the tube. The tunnel is formed by a folded back edge adjacent to the open upper end of the tube. An elastic thread joins the folded back edge of the tube to a portion of the tube there beneath. A cord has a central section within the tunnel. The cord has two free ends extending through end openings to exterior of the tunnel.