Install Backer Rod

What happens here

Take a piece of backer rod and begin stuffing it into the identified wide gap. The backer rod should be slightly larger than the gap itself to ensure a snug fit. Once a section is in place, use a utility knife or other cutting tool to carefully cut the backer rod to the appropriate length for that part of the joint. Press the backer rod firmly into the gap, ensuring it is recessed enough to allow for a consistent bead of caulk over it. This step provides backing for the caulk, preventing it from adhering to the bottom of the joint, which allows for better movement during expansion and contraction.

Goal: Properly insert backer rod into the joint to create a suitable caulk base.