IDIOMS

open one's legs

(idiomatic, of a woman) To open oneself up to sexual intercourse.

Example: 2011, Shanita Ann Johnson, Love Isn't Painful:
  "I beat the shit out of that bitch though, not because she was fucking my man but because she knew he was my man and was still fucking him...well I bet that bitch gone think twice next time before she open her legs to another bitch nigga."
1991, Knut Faldbakken, Insect summer:
  "Pity for you though, all the same, you could have tried your luck there — she'll open her legs for grammar-school boys, sure as eggs."
"But if she's not much to look at anyway," I said, thereby saving both him and me...