I used this Mobile Home Polyethylene Underbelly Repair Tape the other day. It's great stuff.
It's super sticky. so you have to be careful taking the back liner off, but it sticks firmly on the vapor barrier on the underbelly of mobile homes. It makes repairing holes easy. Mobile homes usually have a plastic vapor barrier covering the bottom of the home in the crawlspace that keeps out moisture from the outside. If you have to make a tear to look at your plumbling for example, you don't want to just leave it alone. Moisture can get in, not to mention unwanted critters. This Mobile Home Polyethylene Underbelly Repair Tape makes it super easy to repair. You just need a pair of good scissors. Cut out a size you need first. Then slowly peel back the liner to reveal the sticky side of the tape. Be careful and take your time though. It is easy for it to stick to itself, but it needs to be super sticky to make sure it doesn't fall later on.