Every six months I go to the dentist and park in an underground lot with a clearance sign that sports a blatant typographic faux pas. It uses smart quotes in a dumb way, highlighting hardware and software problems that only an understanding of different quote marks can help us navigate. For measurements like the 7' 0" in this sign, straight quotes, otherwise known as primes, should be used. Those are the characters that correspond to the quote key on your keyboard, but many applications these days convert those primes to smart quotes, also known as curly quotes. That automatic conversion to smart quotes is usually our friend because it makes our quotes and apostrophes typographically correct, but it works against us for foot and inch marks.
This particular case is especially irritating because it inexplicably uses an opening double smart quote for the inch mark—it would normally at least take a closing quote, but ideally should use the straight quote. As I looked into it, I discovered an additional trick of making the straight quotes italic to achieve prime purist nirvana.
This chart gives a quick overview of the different marks and their names. If you want more detailed information, including usage examples and instruction on how to achieve each mark on different platforms, please check out straight and curly quotes and foot and inch marks on Matthew Butterick’s Practical Typography. It’s an excellent resource.