KanjiJLPT N1
Be Bent

be bent, slope, capture

Mnemonic

Deep inside a cavern, you try pitching a tent, but the rocky ceiling is so low every pole must be bent to fit. The whole tent warps into a hooked, curving shape, its fabric sagging against the curved stone walls like a giant fishhook wedged underground.
Additional thoughts
Picture the cavern ceiling forcing the tent poles to curve inward, creating a hook shape that mirrors the kanji. The outer stroke is the cavern, the inner element is the crumpled tent.
Quick recall
A tent inside a cavern must be bent to fit under the low ceiling.

Details

The keyword for 勾 is be bent. This kanji conveys the idea of something being curved, hooked, or bent out of a straight line. It carries the sense of drawing inward or pulling into a curved shape, and by extension can refer to entangling or ensnaring. The character evokes the image of something that hooks or curves rather than proceeding in a direct, linear fashion.
On'yomi
こう、く
Kun'yomi
かぎ、ま.がる