Socks must rise to the calves so that when sitting the ankle is not exposed.

袜子的长度应该都小腿处，这样坐下来的时候，就不会把脚踝给露出来了。

youdao

He tore a long strip from one of his two blankets and bound the ankle tightly. He tore other strips and bound them about his feet to serve for both moccasins and socks.

他从一条毯子上撕下一条长布条，紧紧地包扎住受伤的脚踝，又把另一条毯子撕开裹在脚上，代替皮鞋和袜子。

youdao

But some girls are taking advantage of a loophole in the regulations, which do not set out what kind of ankle socks should be worn.

CNN: A SOCK TO THE SYSTEM

Then, in some trick of the light, or because she sagged her chin into her wrinkling neck, or her too short trousers rode up above her ankle socks as she was sitting cross-legged, Ally saw for a moment the old woman she would become, vulnerable and stubborn, cut adrift.

NEWYORKER: She��s the One

Presto -- the heavy socks defy gravity by clinging to her legs midway between ankle and knee.

CNN: A SOCK TO THE SYSTEM