dude its called a ring terminal. go to walmart or wherever and say i need a ring terminal. its a circle piece made of metal and then connected to the ring is some extra metal where u put the end of the wire into and pinch the wire inside of it.
i just bougt a second one of those cuz my battery connects on the front side and top, i bought one of those took the big wire out of it and put my 4guage wire in there and tightened it back up wroked perfectly..