The casing up must be done in silence in an absolutely clean environment. All outsiders are categorically forbidden to enter this sanctuary with its positive pressure atmosphere. The calibre is placed in the case; dial and hands are delicately fitted; tweezers and screwdrivers sit alongside the casing cushion which the case rests on. After this step, the watches will shut away the secrets of their fine workmanship forever. Once assembled, the watch goes through the many tests and checks which Jaeger-LeCoultre imposes on its timepieces.