noun
door pivot; pivot hinge extensions
Refers to the top and bottom extensions of a traditional Japanese door that fit into sockets in the frame, forming a pivot hinge. A specialized architectural term; compare 枢 (くるる).
See also: 枢 (くるる)
古い日本家屋では、戸のとまらが枠の穴にはまって回転する仕組みになっている。
In old Japanese houses, the door's pivot extensions fit into holes in the frame and rotate.
くるる is a more common reading for the same kanji and also refers to a pivot or hinge, but とまら specifically denotes the door's top and bottom extensions.
The derivation is uncertain. The word likely combines 戸 (to, 'door') with a component related to pivoting or rotating, but the exact origin is unclear.