Context: The informant is the kendo teacher in a kendo club that the collector joins. Kendo is a traditional Japanese martial art and sport. Players use bamboo swords and protective armors. The informant and the collector were at a club party. The collector asked the informant about folk beliefs in Kendo. The informant is Japanese American. He has practiced kendo for thirty years.
In kendo, clothing is in traditional Japanese style. There are no buttons. All parts are tied around the body. When players are fastening their clothing, they should keep the knots (結び, In Roman: Musubi ) horizontal. The knots must not be vertical, because that is only for clothing of deceased people on their funerals, according to Japanese culture.
It is probably common in customs that something about dead people is treated opposite from how it is supposed to be for living people. This may be an attempt to make a clear division between living people and the dead. An example of similar practices: in East Asian culture, for clothing that has two parts of collars, the collar on the left side should always be on the top for living people. Right collar on the top is only for dead people.