A ratio of a proportion, expressed as w:h, where w is the width, and h is the height. To complicate matters, fast-fold screens are usually expressed as height by width, so the ratio must be revered. Standard 35mm slides are 3:2 in horizontal format, 2:3 in vertical, resulting in screens 8'x12', 10'x15', 12'x18'. A special multi-projector format, known as "one over two" using two images side-by-side with one in the center, and results in stage friendly screen proportions of 8'x24', 10'x30', 12'x36', 16'x48'. Standard video format is 4:3, resulting in screens of 9'x12', 10.5'x14', 15'x20', 18'x24'. HiDef video format is 16:9, resulting in screens of 72" x 124", 7'10" x 13'4", 9' x 16', 13.5'x 24', 15'x26.5', 18' x32'. Often a screen is chosen that matches the desired width, and the top is masked down with a valance and or the bottom is masked up with a skirt.The image may also be cropped and sized in the content creation stage, and "edge blending" techniques may be employed to allow seamless images across multiple projectors. The drapery shown above on the right is known as a "Dress Kit" or "Trim Kit", and includes Legs, Valance and Skirt, usually in black velour but occasionally in other colors. For more on portable screens, see The Screen Works and Da-Lite Fast-Fold® Products. For massive sizes (up to 40' x90'), see Stewart Filmscreen Corp.