 so that it wouldn't leak out the ends you have to make sure that the bottom was filled in with sand so you didn't put in too much or you could use a foam backer rod so there's a lot of prep you have to make sure that it's clean enough because this stuff needs to get a bond to the concrete otherwise when the concrete shrinks and the joint gets bigger it's just going to pull it apart it'll pull away from your self-leveling caulk and you're going to have the same