daijs （小学館）, with picture:
https://dictionary.goo.ne.jp/word/末弭/
うら‐はず【▽末×弭／▽末×筈】 の解説
弓の上端の、弦輪 (つるわ) をかける部分。上弭 (うわはず) 。すえはず。→本弭 (もとはず) 

https://dictionary.goo.ne.jp/word/すえはず/
すえ‐はず〔すゑ‐〕【末×弭／末×筈】 の解説
⇒うらはず（末弭）

heianyumigu.com/c/tokusyu/tokusyu010#:~:text=・末弭（うらはず）,はず）」ともいいます。
・末弭（うらはず）
弓の上の先のこと。「上弭（うわはず）」ともいいます。

https://en.wikipedia.org/wiki/Yumi
Ura hazu (top nock)
Moto hazu (bottom nock

末弭	246	81.5%
末筈	27	8.9%
上弭	29	9.6%
上筈	0	0.0%

In daijs with picture. Appears on various diagrams of bow anatomy.  Good exemplar of barely-represented 弭(which seems pretty much dedicated to bow-nocks). 

Considered "upper/lower", wikipedia uses "top/bottom knock", which seems good as anything.  Distinction not usually made in English in any standard way.

Separate potential entry 上弭　うわはず　also attested, but rare enough that it's not worth it to me personally.　 

すえはず seems like a modern mis-reading of an archaic form. Doesn't seem to pop up outside of the kokugo entries themselves. (bare search for うらはず returns archery results, すえはず returns dictionaries).