Abstract: A rotary cutting blade displaced laterally on an adjustable guide beam for cutting vinyl, mylar, or other window treatment material to a desired width and which permits trimming along any length of said material where it may be continuously fed through the present device and the last cutting point reset to permit additional cutting or trimming. A rugged structure comprising a base portion to which a pair of rail arms connected by a guide beam cross member portion is pivotally and adjustably attached. A rotary blade housing body that is simple and inexpensive to manufacture and allows for safe use.