yè Left: body part 月/肉, right: night 夜 (On the roof 亠 is a person 亻/人 watching the moon 月 during the night.) The body part where it is 'night' is the armpit.
yē Left: hand 扌, right: night 夜 (On the roof 亠 is a person 亻/人 watching the moon 月 during the night.) If the hand is in the 'night' it was tucked (into a pocket).