Tricks of the trade for vanity replacement?

[Admiral]

I use lipstick for this very purpose too. Also for marking wall boxes when hanging sheetrock. I've yet to find anything better.

I learned that trick from the guy that installed new door locks on my house about 20 years ago, who used it to mark the deadbolt.  Excellent.

[Snipe Hunter]

I learned that trick from the guy that installed new door locks on my house about 20 years ago, who used it to mark the deadbolt.  Excellent.

That's how I learned it. I worked for a now defunct Home Improvement store and would work with some of the door and window installers when they were swamped. The same guy taught me to use matchbooks to put between the door and frames for interior pre hung door installations and to never drive the second nail before measuring between all diagonal corners. He could replace a whole house of doors in less than 2 hours. Including caulk..

[museumguy]

So what about the next guy?  Are they SOL?

Nope, they make bits for drilling out the pipe that is glued in a socket. This is one that our plumber uses, https://www.amazon.com/Jones-Stephens-So...MFMKD039QD . There are other methods. We only cut the drain line if there is enough pipe to glue a connector on. We don't screw over the next guy, usually it's a plumber contracted by our company. Any extra labor is back charged to our company so if we make a mistake and cut the pipe short, we sure do hear about it. We sometimes call the plumber and have him come over in an emergency and do the disconnect. Such is the case if the shut off valves leak or the drain has issues.

We do think about the next guy.