Smack-dab

 

Smack-dab is not a unit of measurement but is a physical location.   You’ll not see it marked on any map.  Either you know where it is because you’ve been there before or someone else has told you, but it is never written down.

You’ll not even find it along the murky bottom of the Internet.  It is an expression that has been on Earth longer than the cockroach and has spread as slowly and as silently as peanut butter across the country.

Given enough string and the proper coordinates, a person might come close to finding the center, but rarely will they end up smack-dab in the middle.