GREAT STUFF Foam Sealant Kit prevents pests from entering your home by sealing gaps, cracks and holes where they commonly enter the home. It is specially formulated with a bitter ingredient and prevents unwanted critters from entering by creating a barrier and eliminating points of entry. For additional protection, insert Copper Mesh into openings before sealing to block critters and varmints from chewing through. Using the kit is easy. Pop the top off the can, screw on the can onto the gun, open the gun's valve and you are good to go. If the can is not finished after the job is done, leave it on the can and close the valve until the next use. When it comes to the cleaner, however, remove the can from the gun after usage.