I bought five nipples recently at a chicken fair. These don't have the threaded brass part that I've seen on others that would screw onto the nipple itself and keep it in place. They have a rubber one, a kind of bushing, that fits into the hole which you would have to drill out and the nipple fits up into the rubber piece. I have a couple of gallon jugs and also a new two-gallon water jug that I bought from Target. My question is, how do I drill the holes without cracking the plastic. Are all the different brands of nipples about the same diameter? I measured these and it looks like they are about 11/32. I thought about heating up a phillips screw driver and melting a hole in the plastic, or heating a narrow knife blade and reaming out a hole. A drill bit doesn't seem to be the best way. I'm thinking I need to practice on some plastic jugs first. What's the best way? Do I need to glue or caulk the jug where the rubber piece goes in?