What are the three targets for feet in guard?

When playing guard, there are three especially advantageous targets for your feet: inside the elbows, the hips, and inside the knees. Most guards are just names for different ways you position your feet in these three target areas. Spider and lasso guard target the elbows. Collar and sleeve targets the hips. De la Riva and reverse de la Riva target inside the knees. X-guard uses one foot on the hip and one inside the knee.