pointless (academic) degree; meaningless qualification; useless license; (lit.) a grain of rice on the sole of the foot (must be removed, but not enough for a meal)
Examples (2 in total)
そうだ、あしのうらをまずマッサージしよう。
I know, I'll start by massaging the soles of the feet.
あしのうらは暑さや寒さに対して鈍い。
Soles of the feet are insensitive to heat and cold.