This edge-guide works so well for breaking down sheet goods that I decided to dedicate a circular saw to it. I made the base from 1/4x12x30" melamine for minimal friction when making cuts. Take care to secure the rails parallel to the edges of the base, and the saw perpendicular to the rails. Then plunge the circular saw through the base to create a zero-clearance kerf. Remove the saw to adhere the scale tape to the base with the zero mark at the kerf's edge.
Make the guide block to fit snugly between the rails to keep the sliding fence assembly parallel to the blade. Upper and lower fences joined by bolts and locked tight by wing nuts make up the sliding fence assembly. Notch the upper fence to fit over the rails and guide block. Finally reattach the circular saw to the base. The point where the upper fence crosses the scale tape shows the width of the rip.
— Gerry Blacklock, Spruce Grove, Alta.