Left: hand 扌, right: hole, cave 穴 (It is covered 宀 and a narrowing path 八 leads into the cave.), while, during 乍 (image of a saw 乍; cf. 作 where a person 亻used it 乍 to make sth.)
Mnemonic
When a hand makes a hole with a saw, its material is 'squeezed out'.
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