真的巷子：走到底是牆
這是畫面本身。
noun · B2
A narrow street or passage between buildings that is closed at one end, so you cannot walk through it and have to come back the way you came in.
死巷；死胡同
核心畫面
Picture a narrow lane running between two buildings. Standing at the mouth of it you cannot tell anything is wrong; it looks exactly like the lanes that go through. So you walk in, and you keep walking, and at the far end there is a wall. The word lives in that moment at the wall, and not in the wall itself. What it really carries is the distance you covered while believing there was a way out.
可以想成兩排房子中間的一條窄巷。站在巷口看，它跟會通的巷子長得一模一樣。所以你走進去，一直走，走到底前面是一面牆。這…更多收起
可以想成兩排房子中間的一條窄巷。站在巷口看，它跟會通的巷子長得一模一樣。所以你走進去，一直走，走到底前面是一面牆。這個字的重點就在牆前面那一刻，而不在牆本身。它真正帶著的，是你在相信走得通的那段路上，已經走掉的距離。From the word’s history
Wiktionary explains the blind in this phrase as the lack of a through passage: the way out was thought of as the alley's eye, so an alley with no way out is blind. The phrase is attested from 1583, and has been used figuratively since the middle of the 19th century.
Wiktionary 說明這裡的 blind 指的是「沒有通道」：舊時把出口想成巷子的「眼睛」，沒有出口就等於看不見。這個詞從一五八三年開始有紀錄，到十九世紀中期才被拿來比喻。
Wiktionary, entry blind alley (packet source_ref kaikki:3f6f69a190036ae4:1581717468)
Two branches
做法或線索：看起來通，最後不通
把整條巷子的形狀搬到做事上：一樣是看起來會通、走了一段、最後撞牆。
noun · B2
A way of doing something, or a line of inquiry, that looks as if it will lead to a useful result but in the end gives you nothing.
死路；白忙一場的方向