Had to trim a garden gate today, around 2cm from each edge, using a circular saw.
The gate had half lap joints where the 3 horizontal rails met the uprights. Not very accurate half laps at that, they were proud of the surface and edge.
First side I ripped down was a complete dogs breakfast. The proud half laps pushed the rip fence sideways and the base of the saw got stuck on them, causing blade marks on the edge.
Enter trusty sawboard. Completely unaffected by the uneven surface & edges.
Hadn't thought of it before, but it's great for trimming uneven objects, would be ideal for trellis for example - the saw is supported all the time.