Grammar

Most of us don't have a great command of the English language and our grammar is far from impeccable. And yet whenever we notice a grammatical error it sticks out like a sore thumb. Just check out any comments on social media and a good chunk is spent correcting basic level grammar (there vs. their). 

This is just a long winded way to say I know my grammar is weak before I go on to point out grammatical mysteries. On my bus, I often see this sign by the window and always puzzle why "do not drill here" is in quotes. 

Do they know that no one would ever be drilling anyways but some governmental rule makes them have to post the sign (like coffee lids now state: contents may be hot after McDonald's was sued for hot coffee in the 90s). 

Or they know that no matter how many signs they post, someone will drill anyways and that it's all pointless?

Or is it code for something?  Like, this is where we stashed all the extra bolts that came with the bus but couldn't figure out where they went after we finished assembling it and don't want any questions. Plus we may need them later. 

It will always remain a mystery and I will continue to wonder every time I see the sign.