A pair of turquoise and aubergine glazed pottery chiwen roof fragments, Ming dynasty 55.5 cm high (2). Chiwen, said to be one of the dragon's nine sons, has a dragon head and fish tail. It is often installed as a pair on both ends of the main ridge on the roof, facing each other as if to swallow the ridge. In some Buddhist sutras chiwen is said to attend to the God of Rain, hence incorporating it in architecture borrows its fortuitous meaning of avoiding fire. In practical term, ironically, it is used to prevent leaking as it sits at the joint of the main and the diagonal ridges.