...two home-made "ice picks", each consisting of a stout nail or two fixed into a 2-3 foot board.
I'm having a hard time picturing exactly what this homemade set up looks like and how it would be used. Could you explain that a bit? Would the board be held on one end and stretched out or would it be held "sideways" along the lip of the ice, perhaps spreading out your weight along the edge? And where would the nail be along this board?