>>9425406What you might do in a case like that is put the putty on one side (putty being epoxy or similar that isn't liquid and wouldn't run) and coat the other size with petroleum jelly then squeeze the parts together and let the putty solidify, then pull the parts apart and clean/sand the excess putty.
This is how I fixed leg gaps in pic related.
Of course if you plan to paint you will need to thoroughly degrease the part where you put petroleum jelly.
