I've never found them useful. They're meant to run other webbing through, to let you add to a pack's capacity - but there always seem to be better ways. About the only suggestion I could think of would be to weave an elastic cord figure-8 style between the two parallel sets of daisy chains, and use it to secure a jacket or wet raingear to the outside of your pack temporarily. (Check out some packs and you'll see some with the figure-8 elastic rig.)