[Didymus]

You could try double-sided carpet tape. It's got a stiff backing that makes it easy to cut precisely. If you leave the backing on, it would be a pretty strong cutting guide. Stronger than masking tape, anyway. Or you could cut it into complex shapes and use it without the backing.

If has lots of other uses. I stick it to my work table to hold work for gluing. And to a cardboard paddle to hold small parts for painting. And I cut it with a circle cutter and use it as to mask off tires. Sometimes it's tedious to separate the backing from the tape, but otherwise - great stuff!

Ddms