kannonbiraki tobira 観音開扉

1　A pair of swing doors *tobira 扉 designed to meet at the center of a doorway. Often used in a miniature shrine *zushi 厨子, and in a Buddhist altar *butsudan 仏壇. The name is derived from the fact that many altars used to house images of *Kannon 観音. In many cases, each leaf has a central hinge allowing the outer half to fold back upon the inner as shown in the diagram. A plain moulding often runs round the edge of each half of each leaf, creating a paneled effect.

2　The heavy fireproof swing doors used in fireproof storehouses *dozō 土蔵. The doors had a timber framework to which first mud walls *tsuchikabe 土壁, and then white or black plaster coat *shikkui 漆喰, were applied as in fireproof storehouse construction *dozō-zukuri 土蔵造 (see *tsuchido 土戸). The finished door within its fireproof plaster coat was about 18 cm thick. The peripheral doorframe, likewise cased in plaster, had a timber skeleton which resembled a lintel gate *kabukimon 冠木門, with uprights kabukibashira 冠木柱 and a lintel projecting at both ends *kabuki 冠木. It stood in front of the main frame of the building, to which it was fastened back by long iron straps attached to the hinges. The most striking feature of the doors was the stepped profile *jabara 蛇腹 of their flanged reveals, which were designed to interlock precisely both with an identical profile on the frame and with the opposing door, reducing the possibility of flames spreading to the interior of the storehouse through gaps around the doors (for even greater security, these gaps were sealed with mud). The resemblance of the stepped profile of the reveals to the double folded door leaves of the original kannonbiraki tobira (See 1), when the doors stand open, probably accounts for the use of the term in this case.