to embodiments of the present invention will be described with reference to fig9 13 first the coupling protrusion of the bracket is coupled to the coupling groove 345 formed in the rear surface of the fixing shaft 340 and a rotor rotated due to the elastic force of a well known spring is mounted on a spring on a surface opposite the rear surface of the fixing shaft further the winding drum around which a double fabric 110 made of a connection fabric 113 connecting a front sheet 111 and a rear sheet 112 is wound may be coupled and fixed to the protrusion 314 of the cover 310 lower end rods 371 and 372 are provided on the lower ends of the front and rear sheets 111 and 112 respectively each of the lower end rods 371 and 372 can have a cylindrical shape and the same length as the width of the fabric a string provided with a handle may be provided at the lower side of the lower end rod 371 of the front sheet for use as illustrated in fig9 and 10 the lower end rod 371 of the front sheet may be gripped and pulled downward in a state.