Foot and inch marks

Foot and inch marks— also known as minute and second marks, or prime and double prime marks, depending on what they’re labeling — are not curly. Use straight quotes for these marks.

She’s 6 10. wrong

She’s 6' 10". right

Typography purists would point out that proper foot and inch marks have a slight northeast-to-southwest slope to them. True, but those characters aren’t available in most fonts. So straight quotes are the most reliable tools for the job.