只此三根 A Drill A Bow And A Cord
忽喜道：「身上毛都如彼軟熟，只此三根如此硬槍，必然是救我命的。」即便咬著牙，忍著疼，拔下毛，吹口仙氣，叫：「變！」一根即變作金鋼鑽，一根變作竹片，一根變作綿繩。忽喜道：「身上毛都如彼软熟，只此三根如此硬枪，必然是救我命的。」即便咬着牙，忍着疼，拔下毛，吹口仙气，叫：「变！」一根即变作金钢钻，一根变作竹片，一根变作绵绳。
逐句解 Line by line
He brightened: "The hair on my body is all soft and pliant like that, and only these three are stiff as spear-shafts. These must be the ones to save my life."
只 is zhǐ, only — the character drifts toward zhī, the measure word, when read out of context, and the sealed chapters give zhǐ at every one of their hundred and fifty-one sites. 硬槍, stiff as a spear, is Wukong's own comparison and tells you what he thinks with.
So he set his teeth, bore the pain, pulled the hairs out, blew a breath of immortal air, and cried, "Change!"
Both 著 take the light zhe — teeth clenched and staying clenched, pain borne and going on being borne. The whole sequence is five verbs in seventeen characters, and it is the first time in this chapter that plucking a hair has hurt.
One became a diamond drill, one a strip of bamboo, and one a cotton cord.
鑽 is zuàn here, the falling tone — this is the tool, the drill itself, and 康熙 records the split by way of 六書故: the departing tone is the boring implement, the level tone is using it to bore. Every other 鑽 in this chapter is the verb. 金鋼鑽 is a diamond-tipped bit, and 康熙 has a note on the stone itself under this very character.
Three hairs, three parts, and they are not weapons. A drill, a springy strip and a cord are the components of a bow drill — the oldest boring tool there is, worked by sawing the bow back and forth so the cord spins the bit. Guanyin's emergency gift turns out to be a piece of workshop equipment.
That choice is the chapter's whole argument in miniature. Wukong has already tried strength and size against this bottle and the bottle answered both. What gets him out is a hand tool used correctly, and the title has been saying so since the first line: the Mind-Monkey bores through the body of yin and yang.