Post deaf, Razor sharp... (a speacial usage of noun and adjective?)

Please have a look at these sentences :
1.It’s razor sharp.
2.He’s post deaf.
3.It’s nail tough.
I happen to read all these sentence in my book.I suppose it is a special usage of ‘’ noun adjective’’ but I don’t know in which context we should use them and how to use them?

Hi Duc

The only one of your sentences that sounds natural to me is the first one.

The other two would be more natural to me this way:

  1. He’s (as) deaf as a post.
  2. He’s (as) tough as nails. (I would use ‘tough as nails’ to describe a person.)