The part of the body that Sagittarius rules are the hips and the thighs. Let me explain that, in Astrology, each sign is connected to or has an affinity toward and what we call rules, a certain part of the body. For Sagittarius, which is the sign of volition, of freedom, of locomotion, literally the sign of motion, the hips and thighs represent this.
Sexually a Sagittarian is very turned on by and receives erotic messages by having his or her hips and thighs fondled and rubbed and touched and nibbled and stroked very gently. There are many, many places around the hips and thighs to do this. The inner thighs, particularly, are sensitive and send erotic messages.
The inner thigh can be stroked gently and particularly in the act of love making the inner thighs are important because it opens the way to literally having sex. For a Sagittarian, the feelings that are engendered, the arousal that is engendered by lightly fondling and touching and kissing and stroking any part of the thighs inside, outside and the hips arouses a Sagittarian to his or her best performance sexually.