The clutch back's dominance in earring closures isn't incidental. It meets a more demanding set of requirements than it sounds. It's compact, fits any standard post, and works whether the earring is a diamond stud or a long dangle.
The Perfect Fit
Post length matters more than it gets credit for. If it's too short, the back can't grip the post properly, and if it's too long, it extends behind the ear and loosens. Earlobe thickness is the measurement that determines which post length actually fits.