David Boston's training regimen

I was checking out this thread on another website regarding David Boston’s training with Poliquin. It said he did a lot of posterior chain and hamstring work. An exercise was mentioned that was described as a split squat with heels elevated in front of a low pulley. Does anyone know exactly how this is done?

keep reading that thread it is explained

if you’re going to do a split squat with the right leg then grab the low pulley handle with your left arm. Elevate your rear(left) leg on a bench or something. Get your stance close enough so that when you squat down your knee extends out over your toes to hit more quadricep and less glute. Also stick something small up underneath the heel of your lead leg to further isolate the vastus medialis and quadricep.

i also read that thread…but i still odnt understand how it works… i dont kno how the low pully gives u resistance