A poncho "liner" is a military blanket with strings attached all along the sides so you can tie it to the "poncho". I've got several and use them in all kinds of different configuations on my hammock. I've got one that I've added channels to and shockcord and that functions as an UQ. I've got another that I'll tie over my bug netting and use as a wind shield when I'm camping in freezing (and lower) temps. I've used another inside my hammock for additional insulation around my feet. I like these "liners" but I only carry them when "car" camping with my truck near-by. They do add up in weight, so I never use them when backpacking.