Stone Bridge Security And Shipping is safeguarded by a comprehensive multi-layered security system, highlighted by a 90-ton steel cylinder protecting the only entry into the vault. The nine-foot-tall cylinder is set within a 140-ton steel-and-concrete frame that, when closed, creates an airtight and watertight seal. Also, once closed, four steel rods are inserted into holes in the cylinder, and time clocks are engaged, locking the vault until the next business day.