You just need something thin which can hook over the far end of the key.
There are special tools available but they are really just what I said
first. You could make something by cutting a junior hacksaw blade down
thinner, and use it to hook over the back. (The teeth would make a nice
shape to catch on the key part.)
The trick is to manoever it past (over the top of) the pins, or wafers, so
as ...



