He props himself up while she rests her legs on his shoulders in a sexual-linked position. So doing renders anal sex easier. The angle of her sphincter beckons his thrusting movements. By holding his legs, she reaches him better while imposing her pace. Anal sex enhanced by her leg opening, forcibly, squeezing him tightly inside her. A woman who fancies showing off her womanly skills finds in anal sex, a two-fold sex play, either with herself or for their delight in unison.