Foot marks.
No not foot prints. Foot marks.
That's one in the screengrab above.
Looks a bit like an apostrophe. But it's not.
Foot marks are used with imperial measurement.
They are not apostrophes.
Never have been. Never will be.
A good typographer or an old school art director would never allow an ad with foot marks out of the building.
Yet it is quite common today. Especially in digital work.
No idea why. Wish I did.
If you're not sure about the difference here's a handy reference to print out and sticky tape onto your computer.
