If you are using a portable circular saw to make long cuts in sheetgoods, you may know how difficult it is to get an accurate straight cut using only the base plate as a guide. Sawdust blows out over the cut line. You can't reach very well to the middle of a 4x8 sheet to get your eye over the base plate, and you end up grumbling, "There must be a better way."

What you need is a straight edge guide to run the saw against. These are commercially available, but are simple to make for yourself. You'll need two 8' lengths of material, one of solid, clear wood or good quality birch plywood 1/2"x3"x8', and one of plywood or hardboard, 1/4"x10"x8'.

The 3" wide, 1/2" thick piece must have one good straight edge. Either joint a straight edge on solid wood, or use the "factory edge" on a piece of birch ply and cut parallel to that factory edge for a 3" width.

Glue and clamp the two together with the two left edges even and your accurate straight edge of the top 3" piece exposed near the center for the saw's base plate to ride against. When the glue is set, lay the edge guide along a plywood sheet over sawhorses and clamp it down so the bottom 10" piece overhangs its support.

Now, place the circular saw against the straight edge of the top 3" piece and hold it flush to that edge as you run the blade up the 8' length of the guide. You now have a straight cutting edge, pre-set for the width of your saw's base plate (with that specific saw blade…use a standard combination blade to cut the guide).

You can clamp the guide along a penciled cut line and make accurate, straight cuts quickly and easily. Just remember to set the blade depth a little (1/4") past the depth of the material being cut plus 1/4" for the guide base.

Be aware, too, when cutting with a circular saw, the blade cuts into the workpiece from below. It's best to place the workpiece's good face down for cutting operations.

Bore a 1/2" d. hole in one end of the edge guide, and hang it on the wall for easy storage.