"I'm a lumberjack and I'm okay. I sleep all night and I squat all day..." Okay, so maybe that's not really how the classic tune goes, but it would be one way to change up your lower body training.
The lumberjack squat is one squat variation you'll want to try for a bunch of reasons. Because the load is kept off your back, your lower back isn't put under compressive stress. It's also perfect for home gym lifters who don't have access to a squat rack and still want a big basic leg exercise.
Plus, if you're introducing a newbie to the gym, it's a great way to learn proper squatting form without having to steal a 12-pound Body Bar from the step class. The movement just won't feel right unless you keep your chest puffed out and your lower back arched — exactly like a textbook, athletic back squat.
Simply wedge one end of a bar in a corner of the room, or inside a Landmine-type unit, load up the free end with a bit of weight, grab the bar with both hands at chin level, and get squattin'.
As far as the sets and reps, it's as versatile as any squat variation. For beginners, try using 4x6-8 to learn the proper squat technique and body positioning. More experienced lifters with a mean streak could also use 1-2x15-25 as a brutal finisher after any leg session.