I won't mock the question but this is really cut and dry. You don't put foil on your gloves, you put them on your hands. More specifically, your fingers/knuckles. Foil is taped onto the hands to create a harder surface during a fight. Not to mention a jagged surface. You can easily cut the opponent with foil.
As mentioned, the Hanson bros. are seen "putting on the foil" in a classic scene from the classic movie Slap Shot. A real must see really.
In reality, this practice is banned in all levels of play I believe.