I did a quick Google search last night on ABS repair. I found a site (don't remember which one) that recommended using ABS cement. I picked up a couple of cans today and started playing. For some reason, somebody drilled a hole in the vent. App. 1 inch in diameter. This was in the area where there was a towel rack. Maybe they wanted the towels to dry faster! I don't like the idea of combustion gas inside the coach so I decided to practice on this one first.
I placed blue tape over the hole on the front. Then gave a light coat of ABS cement over the hole and tape.
Then I cut and placed a square of aluminum window screen over the wet cement.
I then put more cement over the top. I will check it tomorrow to see if it works out and post the findings.