I guess "chicken lines" have evolved to something more sophisticated than what I remember from the Hobie 18. As I recall, it used to be that a chicken line was a line that went along under the outside lip of the hull and was bungied somehow at each end (or maybe just the forward end). We never used one ourselves, so I don't know exactly how it was fastened. But when sailing in heavy air, you just pulled the line out when you were on the trapeze and held onto it with one hand to keep from being thrown forward.

I can't even imagine wanting to have something like that actually attached to me.

Now that catamarans don't have "lips" any more where the deck joins the hull, maybe that "old-fashioned" type of chicken line is not feasible any more except on the older boats.