It's hard to hold the four tabs on both sides of the SNES controller plug when trying to open it. Using metal tools also damages the tabs a lot. Hence this tool.

Try to put all 4 nipples into the holes, squeeze the tool inwards while trying to pull the innards outwards through the holes on the sides of the plug with a dental pick. It's brutal but I can't image it being any easier without a good tool.

Note the tabs on the stubborn side will still be slightly damaged if you look very closely. But like I said, it should be much better than metal tools.