sen 栓

Also called komisen 込栓. A pin, peg, key, cotter or dowel made of hardwood, usually oak or zelkova. It varies in shape and size depending upon need and placement. It is added to butt or end joints *tsugite 継手, and to angle joints *shiguchi 仕口, for strength and security. Holes are bored where necessary and pins are inserted and may pass through tenonned and indented pieces. The sen may be blind and only partially inserted to prevent slippage. There are many kinds of sen:

1　komisen 込栓 or daisen 大栓. A blind joint with pins slightly off center. See *okkake daisentsugi 追掛大栓継, Komisengama 込栓鎌 is gooseneck joint with pins or a mortise-and-tenon joint used on a penetrating tie beam *nuki 貫. It is characterized by the addition of a pin or key inserted through the head of the tenon *hozo ほぞ, into the top of the pillar for purpose of tightening and strengthening the joint.

2　hanasen 鼻栓 (nose pin). A blocking draw pin used in vernacular houses *minka 民家. For example, a suspended strut tsurizuka 吊束, is joined to a purlin *keta 桁. The end of the transverse beam *hari 梁, in the roof framework is cut into a large tenon that extends through and beyond the outer surface of the pillar. In order to draw the nose of the beam tightly to the pillar and to prevent the pin from penetrating the post or from slipping, the pin hanasen is cut at an angle and is driven through a mortise cut in the extended tenon.

3　shachisen 車知栓, *shachi 車知 or 鯱 are slightly tapered keys placed in haunched or right angle mortises formed by oblique positioning of matching right angle cuts in both the tenon and beam. When these parts are joined, the key's tapered ends are pounded into the resulting slots. The slots may be aligned, half or fully staggered. If two boards are held together by shachisen, only mortises are made obliquely, part on each board, to receive the pin. See *sao 竿, *saoshachitsugi 竿車知継, *isukatsugi いすか継, *saobiki dokko 竿引独鈷.

4　Another type of pin is the yokosen 横栓, a threshold-to-post pin. This is driven horizontally into a groove where the threshold and post meet. See *shikii 敷居.

5　hiyodorisen 鵯栓. A long cotter with a head, kashirasen 頭栓, that passes through the tail rafters *odaruki 尾垂木, where they meet at right angle on each side of the hip tail rafter sumiodaruki 隅尾垂木. It protrudes beyond the rafter on the side opposite its entry. A small pin called a magosen 孫栓 (randchild pin) is driven through the protruding part to prevent slippage and to tighten the pin. It is used in shrine and temple architecture.