if you have a door that needs cutting lengthwise for whatever reason, why go out and buy a fancy door guide when it will spend most of your life hanging on the garage wall? Get a straight 1x3 or 2x4 with a couple of hand clamps, measure from the blade on your saw to the edge of the plate. This distance will be added to the amount of material you want to remove from the door.Transfer this measurement to the door making making sure you lay down some wide masking tape on the less visible side of the door which will be the one you make the pencil mark . Once the line has been drawn, line up your 2x4 on it ,clamp it on both ends and your ready to go! Make a long steady cut, remove the masking tape , sand the edges lightly and presto! Now you can use that 2x4 for something else! cheers,Derek