Most modern RV’s have two sets of waste tanks.  A grey one for all the semi-nasty waste water, from sinks and showers.  The black tank holds all the real nasty stuff, from the toilet.  One of the tasks that follows filling up the tanks is emptying them.  There is a whole sequence to follow when emptying but you want to do it the right way.  Do the black first and then you can use the grey to flush out the hose.  Some times, at some locales, you can just dump the grey wherever you would like.  BLM in Arizona was like that.

Since there are two dump tanks there are two dump valves and they are appropriately labeled but from my normal vantage point, this is what I see:

Now if I bend over:

Oh!  There are the labels clearly marked as Black and Grey.  Wait!  No they aren’t.  They are Main and Auxiliary (Wash)!  Must be a better solution for me.  Like this:

Much better.  Now I can tell what they are and without bending over!  They came with double-stick tape but I had to rivet them…