Examples of exercises for building the quadriceps include the backward drag, barbell full squat, barbell lunge and barbell step-ups. Other exercises are body weight squats and box squats.
To do the backward drag, load a sled with the desired weight, attach a rope to the sled and hold onto the rope while walking backwards. For safety purposes, it's best to do a barbell full squat inside a squat rack. This exercise involves setting the desired height and weight for the barbell, lifting it off the rack and squatting while holding the barbell behind the head so that it rests on the upper back.