Q. Choosing between in or at: When referring to a specific area on a slide presentation, would you say “in the top right-hand corner” or “at the top right-hand corner”? Are there rules that help one determine when to use in or at?

A. Prepositions are tricky! Even fluent English speakers can disagree on which one to use. CMOS 5.195 presents a list of words that usually go with certain prepositions, but often (as in your sentence) more than one works well. When you’re stuck, look up the preposition in a dictionary and find an example phrase or sentence that’s similar to the one you’re puzzling over.