When I was a kid, I didn't have the money or the space to buy a bunch of equipment, so when it came to doing heavy work, I had to improvise. One of the biggest questions to answer was how to do squats? I mean, how do you get a bar loaded with plates over your head and perched behind your back without a squat rack or squat stands?
One way is single-leg squats. They require coordination and a level of strength you really cannot comprehend until you try them. Here's a demonstration on how to do single leg squats: