This is a simple project, and really adds a lot of space. Most campers/trailers/rvs come with a cover for your sink, but some are not very useful. Mine was made of the same chipboard/formica as the counter. I couldn't even use it as a cutting board, and after a few years, being by the sink made the chipboard swell up and become 'unsightly'. Of course, if you buy a second hand camper, you might not even get one!
I decided to make a more useful, durable and attractive cutting board / sink cover myself.