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?

A knife seems less than ideal for this particular purpose, particularly if it's a folder. Considering the diminished dexterity from the cold water and having gloves on plus the force a person would be trying to exert on that knife to pull themselves out, seems very easy to cut up your hand. Of course, you may not feel it at all at the time, but still...

Didn't Bear do a similar experiment one time? Or was that the Les Stroud episode that someone else mentioned? One thing I remember that I had never thought of was that if you're having a lot of trouble getting onto the ice, one last ditch thing to do is splash some water onto the ice and let your arms freeze to the ice. That way, if you pass out from hypothermia, your head is still above the water. Kind of morbid to think about, but an interesting tactic.