Yep, I remember seeing this in a video back in 2008 or so and never forgot it. You can get away with just one 2x4 on one wheel. I have a 89 Toyota with a 3'' lift and a 1 to 64 reduction in the transfer case with modest blocked 32's and this technique got me out of a pit that was up to the top of the tires. Surprisingly effective for how simple and cheap it is.