Assess and Prepare Gap with Backer Rod

area here's a piece of backer rod right here now you know if you fill this up with tower tech and it would actually bond to both sides it would expand really well but if it contracts it's going to push out a big bulge of caulking which is what it looked like before so it's just best to take stuff and some baccarat in there this will give your caulking some backing and just take my knife