What does it mean to tie a red line to a woman's right ankle?

According to the old custom, the dowry of a married woman must be tied with a red line, which means "red line binding feet" (second wife, remarriage is exempt from this custom), which means "everlasting". In modern society, everything is very simple, so the red line is tied to your feet, expecting the old man to help you match your other half, which means "everlasting"