I have a residue on my ruler base for my longarm and I'm not
sure what to use to clean it. It is from the protected cover
that was on it. After I peeled it off it left the residue.

I use rubbing alcohol all the time to wipe off anything that gets on mine even permanent marker

GooGone is a good product. There are others out there that work too.

This is what a teacher told me to use also.

I use non acetone nail polish remover, or goo b gone

Ruler rules
Clean acrylic rulers with a soft cloth and a mild soap-and-water solution. Don’t use solvents, abrasives, or alcohols to clean rulers as they may damage the acrylic or fade the ruler markings. Some of my rulers get a used-tape residue because I highlight certain measurement marks with tape. For these, I squirt dish soap directly on the stickiness and allow it to sit for a half hour or so, then I rinse it off under warm water while I rub the area with my fingertips. It works like a charm.