This triangle is the one you previously traced on the outside of the heel. Let's review. Put your two thumbs and index fingers together in a pyramid or triangle shape. Move your body so you are at the side of the foot you working on. Place these fingers over the side of the foot, with the peak coming to rest under or on that protruding anklebone.
This outer triangle represents reflexes for the hip, knee, and leg. The entire area is a reflex. Thumb walking this region will reflex the leg and feet, as well as the knee and hip. Using the right thumb, walk up the edge of the foot to the waistline. Bring the thumb back and over a bit and walk up again, this time moving into the imaginary triangle. Continue in this manner, filling the triangle from the heel edge.
When the thumb cannot go any farther, you have hit the underside of the malleolus. Start to walk down with the left thumb. The left thumb will walk from the waistline down, essentially repeating the technique from another direction.
Lastly, thumb walk with the right thumb from the side edge up toward the malleolus, filling in the area. Let the thumb walk all over this section, using gentle, small steps. This area may be painful, so always check the comfort zone of the receiver.