It may be a bit difficult to tell what you're looking at, but it is the underside of the vanity sink in our camper. About the time we moved back out of the camper into our home, we discovered that the faucet was leaking.
I told the RV service guy "No problem - I'll fix it myself." I went to Home Depot and got a new faucet in early January, but only completed the successful installation yesterday.
I removed the old faucet without a problem, but connecting the water back up was next to impossible. You're probably thinking Hey - plumbing is easy. Well, I'd always thought so, too. But...
First, everything is up in a corner behind the drain pipe so that if you can see it you can't reach it. Everything had to be done by feel.
Second, the Pex pipe is flexible but very stiff making it a real pain to line up.
And Third, if you don't line it up exactly, it is impossible to get the fittings to seal.
The fittings I'm talking about were both like the one on the left, and after four or five tries I finally got both of them to seal - no leaks - only to learn that the pipes had shifted and I had the hot water going to the faucet handle on the right!
I was sorely tempted to leave well enough alone, but everyone knows the hot water goes on the left, so I marked the hot water pipe with electrical tape, disconnected them both and started over. I got the hot water to line up after a few tries, but the cold water just would not. I said thirty three in the headline, but I honestly lost count of how many times I tried and failed.
I don't know why the manufacturer used those L fittings to begin with, they certainly weren't necessary and, for me anyway, made things more difficult to line up.
This past Saturday, I went back to Home Depot and picked up the fitting on the right. They were into Social Distancing Protocol and had a winding line of tents in the parking lot like some Disney attraction, but once in the store, I found what I wanted and was back out in under five minutes.
When I got home, I cut the L fitting off, installed the Pex to 1/2 pipe fitting then slipped the Pex pipe on. I crimped it down with a hose clamp, and VOILA! we have a functioning faucet again.