Something (in this case masking tape) is likely to bite you on the ass.
Years ago, something like this would inspire much shouting of obscenities. We had a dog at the time with the nickname of Bee-Gee (hard G) who, not knowing why dad was making a fuss, would wag furiously -- probably in an attempt to diffuse things if she was the cause of the swearing. (She did this a lot on Sunday afternoons while I watched the Detroit Lions on TV do one stupid thing after another.) It is still a line heard around here, when I report to Molly something having gone wrong. "Would you have made Bee-Gee wag?" she asks.
After a little therapy, anti-depressants and Zen exposure, I don't make nearly the fusses that I used to. Still get pissed-off on occasion, though. This was one of those times. It's fixed now, but damn it, some of these projects seem to be an adversary from the start. Miss Stearman here has been one of those.