The plaza will be closed to the public during the remembrance ceremony and much of the rest of the day, but it will open from 6 p.m. to midnight for those who want to pay respects and view one of the most evocative observances — the twin beams called the Tribute in Light — from an especially "meaningful vantage point," memorial President Joe Daniels said in an email Thursday to victims' families. [...] to control crowds amid construction elsewhere on the World Trade Center property, tickets and security screening were required until this spring. Since the ticketed, underground memorial museum opened in May, open access has been allowed during days and evenings at the plaza, which joins the streetscape of lower Manhattan even as it serves as a place of remembrance protected by police and security guards.