 A small chamber, equipped with a bell for signalling and a window for viewing the body, was constructed over an empty grave.Watchmen would check each day for signs of life or decomposition in each of the chambers.If the bell was rung the "body" could be immediately removed, but if the watchman observed signs of putrefaction in the corpse, a door in the floor of the chamber could be opened and the body would drop down into the grave.