Things like screwing the plywood under the floor, versus just nailing is just one example.  

"Nail and mail" is sufficient for some cases, but not in others.Typically, actual notice is required, meaning personal service.

Wow @Monika Smith you hit it right on the nail.

Or nail holes where they hung up pictures?  

They're also difficult to install if the roof is a low pitch - and if there's "shiners" (nails poking through the roof), wear a hard hat because you'll probably give yourself a scalp piercing without one. 

Chris Martin hit the nail on the head but if you have to ask that questions (no offense intended - it was a good question) there are probably other questions you should ask or maybe have not thought to ask.  

Travis hit the nail on the head.

You're asking good questions and taking action so I know you'll get it figured out and nail it!

Originally posted by @Chad Benedict:I agree with Rick H. solved their problems.I think you nailed it.  

How much the nails come up matter as to whether you can refinish too.