For us it is nice to be able to reach for a paper towel from the outside of trailer without going in. We can actually slide the little hatch open in the screen door from the outside and grab one without opening the screen door of our 19. It is mounted on the inside door frame.
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So many modifications...so little time.
i thread a roll of paper towel on an extension rod(same as ones used to secure things in fridge while traveling) and place it over the sink area between the fan and lip of upper cabinet...was suppose to be temporary but works so well its now permanent.