Once you have the wipers where you want them, snug them down. Don’t overtighten or you could snap the stud on the linkage. Now check the adjustment. Close the hood and have someone spray water on the windshield while you operate the wipers. (Don’t operate the wipers without water on the windshield or you could permanently scratch the glass). Make sure the wipers are no longer hitting the windshield molding. Switch the wipers to high to check that they are not contacting each other or binding up. If they are contacting, then readjust them until they no longer contact each other. The same applies if they are still hitting your windshield molding.