The fifi hook, a near indispensable tool for big wall climbers to take a short rest, (emphasize short) often has a hole up near the top. (Use of the traditional fifi hook, as shown here, has decreased a bit in recent years, due to the popularity of the adjustable fifi, but this older style still has a place.)

This hole is for you to attach a short loop of cord. If the fifi is loaded, you can grab this cord, pull down on it, and it will lever the hook off whatever it's hanging on. (Sometimes this little “pop” can happen quickly, so be ready for it.) This can be quite handy in certain situations.

I'm using parachute cord tied with a double fisherman's. The orange webbing loop is fairly short, and I have a girl attached to my upper tie in point, that's my preference. Different links and connection options work for different people, try a few methods and see what's best for you.