This technique is basically a "variation drop set", though you could also call it a giant set (3 or more exercises in a row with no rest). You're going to be doing 3 different types of squats, using the different leverages of each variation as the drop instead of reducing weight.

It's a pretty straightforward concept once you see it in action.

1. Start with Front Squats - do as many reps as you can - use a weight you can get 8 to 10 reps with. This is the toughest variation.

2. Rerack the bar and go directly to back squats with a fairly narrow to medium width foot placement with the same weight. Do as many reps as you can.

3. Finally, set your feet out wide and do as many more reps as you can - no need to rerack the bar here - just go right into it. This is the position where you will be strongest at.

By the time you're done with these 3 squat variations in a row, your entire lower body will be pretty well trashed. It's a great squat giant set!