how to repair the trailer underside material

cut with sharp knife only cut three sides. Punch holes in both edges of three cut sides and use zip ties to close it back up.

I recently had to cut mine open to service a tank. After cutting out and removing the coroplast (square opening 18" x 18"), I went to a local sign shop that makes vinyl graphics and they gave me a 24" x 24" piece of black coroplast (used to make vinyl signs), for free. I placed the new piece over my opening and sealed it up with gorilla tape. Has held well and now I have an access hatch for next time I need to get in there.

outnabout wrote:
I need to repair a tank under the trailer. It is covered with a corrugated plastic material that is one large piece covering the bottom of the entire trailer. I need to cut it but don't know how to repair the cut.Any ideas?

The plastic is called Coroplast or Correx. It does not glue well, but Gorilla tape may work for you.
If you want to replace it, 8'x4' sheets should be available from a sign printer near you.
I get it from Laird Plastics in Detroit. About $12/sheet of 4mm. All kinds of colors.

Mine has screws around the edge. I unscrewed it and removed the whole thing. I had to access the pin for my spare tire winch on the road side. I sliced it with a knife and just used some black tape that I had with me. I like Gorilla brand but if all I had was duct tape I'd use it. Black just makes it harder to see.

cut it get a 1×4 put accross the seam or a thin sheet of plywood aluminum and screw into it using fender washers and screws

When we worked on ours, we used several pieces of GORILLA TAPE to repair the work area. It has worked for us for over three years without replacement.