in painting is cutting a straight edge. use painters tape and you will have no problem. this low tack tape can be left on trim for several days and then easily removed without a lot of tugging and damaging the trim. we use frog tape for a sharp clean line. look for the green frog!
if you have left tape on to long, use a low setting on a hair dryer, warm up the tape glue and it will pull away nicely, then clean up the remain glue with a little paint thinner.
for what it cost, maybe a hair under 8 bucks, this tool is a painter’s favorite. from cleaning roller 