Q. For catalog copy, how would I write inches symbols with a period at the end of a sentence? (The client wants symbols rather than to spell out inches. That is nondebatable.)

5'' × 4''.
5'' × 4.''

The client says it’s the latter. I say NO WAY. I think the hash marks are not to be confused with an end-quote mark. Please!!! Please!!! Can someone help me out here?

A. Hang on! We’re coming! You are right: quotation marks are irrelevant. The inches symbol must be closed up to the number, which puts the period at the very end, after the entire expression: 4″ × 5″. Also, please note that the symbol for inches is the double prime (″), not double quotation marks  (”) or straight quotation marks (") or (gasp!) two single quotation marks in a row ('').