thickness from about 1 to about 5 mils the sun screens preferably are provided with highly reflective surfaces e g colors or opaque additives can be incorporated in the plastic or the surfaces of the plastic film can be metallized to provide maximum heat and radiation reflective properties as shown in fig3 the frame of each holder includes a center section 26 which is formed by a pair of spaced apart end plates 24 which form a center compartment 54 the ends of the roller bars 48 of adjacent rollers extend into the center compartment 54 and hand wheels 56 are fixedly secured to the ends of each roller bare the hand wheels 56 are of sufficient diameter to extend beyond the center plates and a center cover 58 can be placed over the center compartment the center cover has the same shape or contour as the cover plates 38 and has a pair of adjacent slots 60 through which the hand wheels 56 extend permitting a user to manually rotate the roller bars 48 raising and lowering the sunscreens preferably the center section extends downwardly beyond the lower edge of the holders 10 and 12 and has one or more through apertures 62.