I'll second exactly what Jim Felder said, he describes exactly what I've
been using for about 15 years in my Westies.  This looks like the one I have
*
http://tinyurl.com/4d6kb8z*
but mine has a different name on it, looks like Thetford has taken them
over.  Being able to tuck it under the lower bed overhang has been important
to me, Keeps it out of the way. I used the first one I had until about two
years ago and replaced it with an identical model when they were on sale at
West Marine.