A word of caution to the TL owners.
I pulled out the water heater today to fix it. There was no putty tape used. Just the bead of caulk around the rim. This is a leak and delamination waiting to happen. They did have the opening coated with black undercoating or something, but that is not a substitute for using putty tape.
I am going to pull off some other things to put putty tape behind them in case don't have it. Namely the fuel hatch, electric hatch, and range vent. I was able to find that the fridge hatch mounting used putty tape, because I could stick a finger around from the back side and feel it. I don't know about the furnace or any of the compartment doors.
Why they would use it on at least one thing, the fridge, and not the water heater, is beyond me. I'll report on the 3 plastic things after I do them. One thing for certain, we should maintain sound caulking around all the moldings. It might be the only line of defense in some cases.