The deadlift split squat is a great low body exercise if you want to really focus on the quads. This is a constant tension movement – the quads never get a break, and that's great for hypertrophy.
Simply split squat or lunge over a barbell, grab the bar, and stand up. Switch legs and repeat for reps. Focus on your legs, particularly your quads, and minimize lower back action.
As a bonus, this variation requires more torso stabilization so you'll get some core work too.
The Fortress believes there are four fundamental directions a weight must be pulled or lifted in order to build a kick-ass back. He calls it his Directional Back Training Principle and it has nothing to do with North and South.