This foam backer rod works great to fill larger gaps prior to applying cocking sealant. The foam is very flexible and can be used to fill even smaller cracks if you use a took to firmly press the backer in place (I used a plastic scraper to press the backer into a small crack). I used this backer to fill a large gap around a door frame in the old house we are renting because the framework has apparently shifted over time. I then filled the crack with a brown wood cocking sealant and the crack is no longer noticeable.