Trap adapter question

[jwbr]

When installing a trap adapter how far out should I rough it in? Should it come out half an inch from the stud so it ends up flush with the drywall? Will an escutcheon cover that and the trap that gets inserted? This is will not be covered by a vanity etc. so I'm trying to get it as clean looking as possible.

[hj]

Ideally, just the slip nut should be exposed, but a proper "deep escutcheon" will cover it even if it is out a bit more. It does NOT cover the "trap".