Use Thumb Gum around all sorts of openings!
Updated: Sep 22, 2019
Thumb gum or electricians' putty is used to fill any openings that you don't want permanently sealed, because you eventually will have to have the AC unit replaced, or redo the hose bib or plug a hole for a fitting in your furance. Plus it's the adult version of PLAY DOH and therefore very satisfying to use! Click on image for link.