Take a look at this photo. I had a plumber do the work, but now I am a little concerned. I bought a cap/cover ( forget the correct name of it) to put on the wall which the water copper line coming from wall, which goes to valve then to the toilet. He made the copper tubing too short and could not get the silver backing plate on the wall between the valve and the wall. So he did not install it. I guess, I am concerned because if I need to replace that valve in the future, I would have nothing to work with. Can you look at this and tell me if it is too short or should I just leave it?

If it ain't leaking leave it alone. If necessary it can be replaced, you just can't have the escutcheon, but pretty neat looking hole. The escutcheon is for looks only.

Not to worry! The chrome cover plate is called a " escutcheon plate" and is just there for looks. Charging out the angle stop's a five minute job. You simply use the old ferrule and compression nut to mount the treplacement angle stop. If the lack of a escutcheon plat disturbs you they make a 1/2" "split ring" plate that you can attempt to slip behind the compression nut. Good luck, Tom

At this point you will probably need to leave that shutoff. It is a compression fitting that has a sleeve that is compressed to tighten shutoff on. I have assumed that you cannot pull pipe forward even a little... right?

Only other option here is to see if plumber can completely remove the shutoff... INCLUDING THE COMPRESSION SLEEVE and nut... and then try to install a solder type angle shutoff with a bell flange. BUT if compression sleeve cannot be removed.. unless you want to open wall (other room)... you are stuck.

Do not worry that it will be an issue in future as the shutoff looks to be installed fine (no leaks)... just missing the flange (or escutcheon is another name for flange). If need to replace in future would just replace the angle shutoff... not the compression nut and sleeve... so no issue there.

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I agree, you can probably pull the pipe out about 1/8" of an inch and install a split flat flange.

If not, you can get a split flange that might fit over the nut. If you want it to look pretty, you can fill the are a between the flange and the nut with grey plumbers putty or latex caulk.