A hanger is a bite detector that hangs from the mainline. They consist of a line clip attached to a highly visible bobbin. This, in turn, is linked to either a chain (similar to those used to attach sink plugs) or a length of dacron cord. Then the chain or cord is attached to a link that allows the hanger to be clipped underneath the bite alarm. After casting, the mainline should be pulled tight, the rod placed upon the alarm and rest, then a little line should be paid out so that when the hanger is clipped to the mainline, it pulls the line down at a slight angle. You will know when you have a bite as the hanger will rise towards the rod.