KanjiJLPT N1
Rope

hawser, class (genus), rope, cord, cable

Mnemonic

grandma decides to mount the tallest sea cliff in the village. She loops a thick rope around her waist as a lifeline, the kind used to moor ships at the docks below. Gripping the rope with iron determination, grandma begins to mount the sheer rock face hand over hand, proving she's the toughest climber alive.
Additional thoughts
Visualize grandma scaling a cliff with a heavy ship-mooring rope tied around her. That thick, twisted cable is the organizing lifeline holding everything together—echoing the kanji's sense of a guiding framework.
Quick recall
grandma mounts a sea cliff secured by a thick rope lifeline.

Details

The keyword for 綱 is rope. This kanji refers to a thick, sturdy rope or cable, often one made of twisted fibers used for heavy-duty purposes such as mooring ships or in tug-of-war competitions. By extension, it also carries the meaning of a fundamental principle, outline, or guiding framework, as in the main "rope" that holds things together. In biological classification, it is also used to denote a taxonomic class, reflecting the idea of a broad organizing category.
On'yomi
こう
Kun'yomi
つな