Running back through the archives resulted in the suggestion that I use the jigsaw upside down. This has done wonderful things for my accuracy, but sometimes I have to mark the flat surface for my cuts, which means I have to use the jigsaw from the same side that my marks are on.

In this case, I take the time to scribe guide lines, either a center line, if I can afford half a saw kerf, or very careful saw edge lines, on the base of the splinterguard, that little replaceable piece of clear plastic that serves to prevent chipping and rip-up around the blade. A horizontal line to show the front of the blade travel also helps.

When I'm looking through 3 or more layers of refracting plastic (eye protection, the upper plastic guards and the chip guard), it helps me make better sense of where the saw is relative to my marks.

I initially suggested that Festool should scribe in the center line themselves as part of making the piece, but after thinking about it a bit I realize that it's better for me to account for saw blade thickness and whatever else I need to.