Abstract: A flexible adjustable wedge of tetrahedronal structure is provided wherein four swivel-jointed arms are attached at their respective ends by pin connections. Flexible adjusting arms provide dimensional stability by interconnecting either opposing corners or opposing arms of the tetrahedronal wedge. The adjusting arms are provided with some degree of flexibility in order to allow the wedge to automatically conform its size to minor variations in the flat width of the film passing thereover. Where changes in overall size of the wedge are desired, the adjusting arms can be easily lengthened or shortened.