An optical film having structures that vary in height along their length where the variations have a nominal period of less than forty times the nominal height of the structures is taught. For this purpose, a memory 50 holds four 8-bit multivalue data per 1 word, and bit plane coding processing is made by 4\xd74 multivalue data. The drag strap includes an adjustable connector system for quick attachment and adaptability in securing the strap to an injured person. Each of the lever arms is provided at the lower part thereof with another magnet, which is exposed to the lower surface of each of the lever arms. The other shaft is separate from the input shaft.