For one reason or another, we all end up having to trim doors with a circular saw. Despite using precautions such as guides and tape to protect the work, many saws leave an unsightly streaking along their path, spoiling an otherwise unblemished job. Well, my saw was one of the guilty ones.
To avoid this problem, I now place a continuous layer of clear contact paper on the base of my circular saw. I cut out a slot for the blade and leave a -in. overhang at the rear to act as a pull tab. The contact paper has a clean, smooth surface that glides easily over a workpiece without leaving a trace. When the contact paper gets worn and needs replacing, it comes off easily with a tug on the pull tab.
MacGill Adams, Anchorage, AK