To keep a male slave after 7 years, we strike through his ear with a nail. But for a female slave, the text says (Devarim 15:17) וְאַ֥ף לַאֲמָתְךָ֖ תַּעֲשֶׂה־כֵּֽן׃
"and the nose, to your maidservant you should do thus"
Why would the instruction be to do thus to the nose of a woman, but the ear of a man?
As a secondary question -- I don't know if this should be separated -- do we make allowances for less efficient work by a male slave after seven years because he is attached to a wall, or is walking around with a piece of door post permanently affixed to his ear?