Squat heavy on a fixed track.
Set your feet a touch forward so the fixed bar path stays over your midfoot.
The fixed track lets you do something a free bar never allows, set your feet slightly in front of your body and squat with a bolt-upright torso. That position drives the knees forward through a big range and pours the work into the quads, with the glutes assisting out of the bottom. Add the built-in safety hooks and it becomes the squat pattern you can push hard without a spotter or a balance battle.
It is a different lift with a different job. The barbell squat trains the whole body and the skill of balancing a load, the Smith version isolates the leg work by deleting the balance demand. For quad growth it is genuinely effective, for total strength the free bar still rules.
Because the bar can only travel straight down. Planting your feet slightly forward lets you sit into the squat while the bar tracks over your midfoot, copying the balance a free squat achieves by leaning. Feet directly under the bar force your knees and back into awkward angles.
To parallel or below, same standard as any squat. The machine makes depth safer to chase since the hooks are always a wrist-twist away, so there is no excuse for quarter reps.
