noun
sleeve length (kimono); distance from center back seam to sleeve edge
A specific tailoring measurement for kimono; not used for Western clothing.
着物を仕立てるときは、裄を正確に測る必要がある。
When making a kimono, you need to measure the sleeve length accurately.
この着物は裄が少し短いので、直してもらおう。
The sleeves on this kimono are a bit short, so I'll have them altered.
袖丈 is the vertical sleeve length from shoulder to hem, while 裄 is the diagonal measurement from the center back seam to the sleeve edge, specific to kimono.
The kanji 裄 is a 国字 (kokuji) created in Japan, combining 衣 (clothing) and 行 (go/line), referring to the line of the sleeve.