The Quad Rock is a great drill for driving in the patterning for a proper squat. Note the knees can't track forward excessively and it forces us to sit the hips between the heels.
We can improve the pattern by adjusting the feet higher on the wall.
Skip to the 1:48 mark here for a video demonstration.
This is perfect for someone who says they can't squat deep.
Driving in the proper patterns will carry over into complex exercise movements.
Remember to keep the feet flat on the wall. In the deepest part, drop the chest toward the ground. Don't allow the low back to round.