The third principle is proper behaviour in the completed house. For example, the threshold is believed to be inhabited by "a household guardian spirit", therefore, stepping on it is prohibited. If residents of the house do not follow this precept, spiritual protection will disappear. Another example is that if someone sleeps under the girders, it is believed that ghosts will cause them difficulty in breathing. Taken together, all of these observances serve the purpose of making houses sacred places and pleasing "good" spirits in order to receive their protection against "bad" spirits.