Sill Sealer is a polyethylene foam, commonly 3-1/2″, 5-1/2″, or 7-1/2″ wide by 50′ long, typically placed between the sill plate and the foundation of a structure. The purpose is to gasket by resisting moisture, resisting passage of air, and help seal out insects.  It does not require adhesive to keep it in place, but this can help from the product moving during sill plate installation.