耂 is the bent-elder shape that sits at the top of characters about age, ancestry, and seniority. Read it as 老 with its lower body and walking stick chopped off so a second component can fit underneath. The pedagogical name lǎozìtóu means 'old-character top'. Never written alone.
history
耂 is the calligraphic compression of 老, originally a pictograph of an elderly person leaning on a cane. In top-position the cane and lower body drop away and only the bent torso and long hair survive as a slanted top stroke crossing two near-horizontals.
usage
Age/elder cue at the top: 考 (test — originally a deceased elder), 者 (one who / agent suffix), 孝 (filial piety — old over child 子), 老 itself when stacked.
