CIRCULAR SAW GUIDE
I am amazed at the interest in guided saw for ripping up sheet goods. People spend big money on these when you can make your own for a just a few bucks and most likely from scrap in you shop. While is doesn't have a fancy name brand on it, it works perfectly and I would rather have that money to spend on wood.
I recommend you make two saw guides. One 4 foot long and one 8 foot long. It makes ripping sheet goods down to size a simple matter. This is picture of my 4 footer. I think it is actually 4 1/2 feet which is good if you have the material. All you need is piece of hardboard or any other thin sturdy stock that will stay flat and a 3-4" wide straight board. You can use plywood but I don't like it because it can bow on you.
Make you a guide block and cut on edge as straight as you get it. If you have jointer joint one edge. You can hand plane it or what ever method you prefer. Just make it straight as possible. Also be sure and make it wide enough to clear the motor on the saw. This leaves room to use tall clamp if you need. Check your motor clearance on your saw, if you using 1" stock like I show you will probably want to plane it thinner so your motor doesn't hit and limit the depth of cut.
Cut the sole (bottom piece) too wide! This is important. Glue the two together and let it dry. Once it is dry you need to cut off the excess. Clamp you guide down to something sturdy like a bench, place your circular saws sole against the guide block and trim the sole plate of the guide to width.
Now when you need to cut down some sheet goods just mark the width and clamp down your new FREE guided saw. Clamp it so that the line you marked is just under the edge of the sole. Since your blade cuts right on the edge you can easily line us the saw to the exact width you marked. Just make sure that the piece your wanting to keep is on the left side if you standing behind the saw. That way if you let the saw slip off the guild block you have cut it over size and not to small. It's simple to just back up the saw and go over the spot you missed. Once you use this a few times you will wonder how you got by without it!