In the 'overhead'? Not sure I understand. In the overflow maybe?
Usually the easiest way to trap an eel is to put a length of PVC in the tank. When it goes into the pipe to hide, place a net on either end of the pipe and lift the whole thing out. Be sure to have a bucket or whatnot, available and ready - and have a lid too - because it can and will exit the bucket quickly as it will be agitated.
If it's in the overflow - not sure about that but you'll want to be careful it doesn't jump out of there and onto the floor.
Jenn