Oh hey, trick I learned at the dojo? Hold your hand flat, palm down so your fingers are sticking out?
Then curl your middle finger a little and cross it over so you’re pressing down on your pointer at the base of the nail
Like this:
There! Now your fingers are sturdy and powerful enough to thrust-poke into someone’s eye socket, scoop along the side of the eyeball, and gouge their eye out.
Your sensei was perhaps overestimating the security of the human eyeball in its socket. Your index finger is sufficient without this.
Thrust, miss, and hit the brow or other bone with one unreinforced finger and you’re liable to bend it contrary to the joints and jam it.
