In a recent CrossFit class, we were working on overhead squats and snatches, and our coach Laura Matuszak with Champlain Valley CrossFit had us find a wall and do this squat stretching exercise. She said for those with very tight shoulders, facing a wall encourages you to lower down into a squat with your torso in a more upright position. It also helps you open your knees out wider, increasing your hip flexibility, and improving your squat form.
This exercise will benefit all variations of squats, including barbell front and back squats, as well as squats with dumbbells, a kettlebell, or a medicine ball. Doing squats facing a wall is so much harder than doing it without because it forces you to lean back and keep your torso up so you don't bump into the wall. The deeper you can lower your hips and put weight back into the heels, the more you'll work your hamstrings and butt.