Regular office hours for both 71st Street and 91st Street brownstones are Monday through Friday from 9:00 AM to 5:00 PM, and Saturdays at 91st Street from 8:30 AM to 5:00 PM. Each person who enters Prep’s work locations must fill out Prep’s COVID-19 self-certification form before entering the building. Masks are optional. Unfortunately, with very few exceptions, outside guests will not be allowed into the buildings. Thank you for your understanding.