A poncho is an essential component of any survival kit, and as such, it can be used in as many different situations and ways as you can imagine. One of such ways is that of a blanket; there are some ponchos with inner liners that can actually work exactly like blankets, but in this case we are interested in something a little bit different: Our poncho blanked, instead of covering our body right on top, will cover our sleeping bag.
You might be asking what do we intend by doing this, but in reality it is a very efficient way of using the kind of gear that you could conceivably carry with you in any sort of excursion. The method just consists in placing the extended and dry - pay attention to this or you will end with your bag soaked - poncho on top of your sleeping bag like a regular blanket. You go into the bag, of course, and you will have the poncho on top of it.
The interior of a survival shelter in a rainy day; sleeping bags have been covered with ponchos.
This will create an additional isolation layer of air on top and around your sleeping bag, increasing the heat retention power of your gear. The poncho will also protect you from moisture, wind and even dust.
Really, there is no secret in this technique but surprisingly, most people that start bickering about cold nights on camp breakfasts actually have such gear at hand but never think about using it. If you don't have a poncho other items will do, like plastic sheets, cardboard, and even car carpets. In the case of a waterproof poncho or any other similar film or cloth, you get an expedient survival shelter by using it as a blanket.