三尖頭的鑽 A Three Cornered Drill
挨到三更時分，行者弄個手段，順出棒來，吹口仙氣，叫：「變！」即變做三尖頭的鑽兒，挨櫃腳兩三鑽，鑽了一個眼子。收了鑽，搖身一變，變做個螻蟻兒，𧿼將出去。挨到三更时分，行者弄个手段，顺出棒来，吹口仙气，叫：「变！」即变做三尖头的钻儿，挨柜脚两三钻，钻了一个眼子。收了钻，摇身一变，变做个蝼蚁儿，𧿼将出去。
逐句解 Line by line
Waiting it out to about the third watch, Pilgrim worked a trick: he slid the staff out, blew a magic breath on it and called "Change!"
The same word-boundary trap as earlier in the chapter sits here. 行 is xíng, part of Pilgrim's name, but it stands straight after 時分 and those two characters happen to make a word meaning a branch office, which pulls the reading the wrong way. The break falls between them.
It turned into a three-cornered drill, and at the foot of the chest he bored two or three times and bored a hole through.
The same character appears three times in one line and not with the same reading. As the tool — a drill — it is zuàn; as the act of boring, twice over, it is zuān. 兩三鑽 counts strokes of the action, so it keeps the verb's reading.
He put the drill away, gave himself a shake, turned into an ant and scrambled out.
The verb at the end is the one that carried Bajie into the chest a few passages back — the rare vernacular word for scrambling, with a direction after it. It went in and now it comes out, which is as neat a use of a rare character as the chapter offers.
The staff that fought the armies of heaven has been turned into a hand drill. Pilgrim's inventiveness in this chapter has run entirely to the domestic: needle and thread, a false fast, a moth, a rat, and now a bradawl.
And the escape is quiet. He does not break the chest, which would give the game away; he makes one small hole and leaves as an insect, so that the official band across the lid is still intact in the morning.