plumbing
I'm installing a new p-trap for a vanity that is roughed in. I'm trying to get the trap adapter as close to the wall as possible, so the escutcheon will cover the adapter (it will be exposed), but there is some sort of collar around the pipe where it comes out the wall: 
Is there some way I can remove this collar so I can get my adapter up next to the wall?
A 1 1/4" female FIP adapter worked perfectly. As soon as I saw it, I was embarassed for not having thought of it earlier.
I used some teflon tape, screwed the FIP adapter onto the adapter coming out of the wall, then just glued my 1 1/4" pipe directly into it. No reduction in pipe sizes, and 100% ABS parts.
You'll need to install a drain assembly. In a bathroom, pop-up drain assemblies are common.
Here's an image of the drain assembly, with all the parts labeled.
(source: naturalhandyman.com)
The tailpiece of the drain assembly, should attach to the trap assembly. If the trap is too low, an extension can be used.
When installing the drain, put a bead of plumber's putty around the drain hole of the sink. Then bed the drain flange in the plumber's putty. From below, install the washer and nut, and thread on the tailpiece. When you tighten it down, the excess plumber's putty will squeeze out. Use you finger, or a rag to remove whatever oozes out.
Best Answer
That is a 2" tee with a reducing bushing glued into it. You will want a "deep box type escutcheon" which will bell over the fitting and hide it. They look like this: