harmonic positions, as well as a reference point to note position, called hui 『徽』 ("insignia"). They are roughly the same size, but the 7th hui in the middle is usually slightly bigger. If the hui are too big, then it is considered vulgar or ugly. The book Yugu Zhai Qinpu is perhaps the most famous book that describes in detail the construction method of the qin. Storage Considerations Generally, the qin should be stored in an appropriate climate. That is, a constant environment. Sudden changes may cause it to warp or split at the joint. Generally, the appropriate climate to keep a qin in depends on where it is manufactured (mostly, in China, which is humid). The air temperature is best at around 20-24°C, with a humidity of around 50-70%. If the temperature is too high, then the glue may melt or soften, causing the joints to split (in the worst case, the edge of the qin cracks open). If the humidity drops too low, typically below 25-30%, then the wood may warp and/or crack, either internally or externally, and maybe the joints could split. Some players, particularly in dry countries or in countries that have a very dry summer, obtain a humidifier to protect the qin from damage by correcting the humidity level of the room in which the qin is stored. The qin must always be placed vertically and not horizontally (i.e. resting on the goose feet and/or tuning pegs), otherwise the qin would gradually curve, making it unplayable. That is why the preferred way to store a qin is to hang it up on a wall, away from sunlight. The weight of the instrument pulls it straight and stops it from curving (though it might curve or wrap anyway if the climate is not constant or the wood is not sufficiently seasoned or cured). Sometimes, the player may attempt minor repairs to the instrument (major repairs like structural faults and splitting of the joints, warping of the wood, etc. are best done by professional qin makers). Minor repairs include re-lacquering areas of the surface of the qin that have had the lacquer chipped, re-patching areas of the surface where the lacquer is worn causing "running-cloud markings", repairing cracks in lacquer, etc. Because these are relatively minor and can often happen due to ageing and constant use, it is more easier to do repairs by oneself than call