Greg's jerk blocks could also function as plyo boxes.
http://www.cathletics.com/articles/i...ty&shortyID=52
Or the crossfit articles are below (google searched "plyo box construction")
http://library.crossfit.com/free/pdf...plyo_boxes.pdf
Lincoln's original thread before he wrote the guide
http://board.crossfit.com/showthread.php?t=12749&page=1