If you did not bring your tent along to sleep in, but would like to have one, you can make your own in a minute. All you need is your paraglider, two sticks, and a pair of (thick) socks.
Search two sticks, about 80 cm long. Choose sticks that are strong enough to support your makeshift tent, but light enough in order not to damage your head should it collapse. Pull a thick sock over one end of each stick. Better use the clean spare ones that you brought along. The ones on your feet should stay there to keep those warm. If you insist on using them nonetheless, be aware that they could chemically affect your glider's fabric.
Now unfold your glider in such a manner that you have an area large enough to sleep under, but small enough as not to wet too much of the glider (dew will settle on your glider as the air cools during the night). Make it a bit wider near the shoulders, especially if you are the body-building type.
I do not want my feet to get trapped in a cell opening, which is likely to damage the glider. That is why I prefer the trailing edge at my feet and the leading edge at my head. This also has the advantage that the far end of the tent is closed off from the wind if your feet are upwind. This seems illogical considering the opinion they are likely to ventilate after a long hike. But having them downwind would give the wind the opportunity to enter your tent near your head (you need some ventilation in order to breath) and eventually blown it away if the wind gets stronger than a light breeze. Your glider has been designed to fly, remember? But if you insist on having you head upwind instead if your feet, then you better be prepared to hold the leading edge down with your hands or quickly grab it before the glider flies of.
Place the sticks under the unfolded paraglider, with the sock-end up (the socks prevent the sticks from piercing or damaging the glider fabric). To have more stability, you could try sticking them in the ground or steadying them with stones. The sticks should now be about 30 to 50 cm from the leading edge, about one metre apart, so that your body fits in between.
Now position your backpack across the (leading edge) entrance of the tent, 20 to 30 cm away from the sticks, and let the leading edge of the glider fall on it. Instead of using your backpack to close the tent, you could let the leading edge hang down all the way to the ground. But this usually goes at the cost of warm feet, unless you have a short body height. In my case, the glider's cord is only slightly more than my body height, so I use the backpack.
You could turn your paraglider 90 degrees in order to have a tent that is longer than your glider's cord allows. However, this somehow seems to end up more messy most of the times, since their is no straight line (the cord) from the sticks to your feet. It also has the drawback that it is much wider than needed, unless you fold in the excessive with. In other words, it requires more effort, while the result of this extra work is often questionable.
This tent will not keep you dry when it is raining (I could be wrong though, I never had the courage to test it), but it will keep you warm and at the same time keep out those nasty mosquitoes, flies, wasps, and other tiny creatures that make your bivouac an annoyance instead of a well deserved rest. Unfortunately, bigger creatures such as spiders, snails, snakes, lizards, mice, toads, ermines, rabbits, hares, cats, foxes, dogs, wild boars, deer, cows, humans, horses, and dinosaurs will usually find a way into your tent as the night progresses. If that happens, just remember that your makeshift tent is not a real tent, but a clever compromise with only a minor drawback (or two) that you can happily live with. Intruders will usually listen when I tell them to get out (except for some deranged dogs I have encountered), but they might need some incentive or coaching, for which one of the sticks might come in handy. In case of an emergency, the wooden sticks can also be uses as weapons to fend of anything that intrudes your tent. Only use in a real emergency, since this action makes the tent collapse completely!
<<< Added on 2011-05-15 >>>
The main reason for doing without any tent so far, is that they all add weight without offering me what I want. I am looking for a light emergency shelter that helps me through the occasional weather discomfort. Not a heavy (even the lightest tents are one kilogram or more), temporary home suited for sitting out the bad weather for days on end. Bivy sacks come close, but have no room for my gear and offer little ventilation. The larger ones possibly could, but seem more like a 'solution' that combines the disadvantages of a tent and bivy sack (heavy, no room), rather than their respective advantages (spacey, lightweight).
Since I couldn't find a solution that suited me, I decided to make my own. The following criteria where used as a starting point:
As you can see, I don't demand a lot. On the contrary. I want as little as possible. All lightweight tents that I have seen offer more than just basic shelter. Consequently, they were more voluminous and weighty than needed. A lightweight tent is no match for a mountain storm. And if it is storm-proof, it is probably not lightweight anymore. Severe bad weather makes me prefer solid shelter, such as cabanes or caves. So, why would I need a heavy storm-proof tent? All this may be ostrich reasoning, but I simply want a lightweight roof over my head in order to keep me dry and out of the wind. Nothing more.
This desire resulted in a green tunnel tent, supported by fibreglass rods. It is seen here in the middle of a breakfast, the yellow flowered plants in this case. The leaves are often a bit bland, but the stalk has a nice aniseed taste to it. The yellow flowers too, though a bit less, but these often hide little creepy insects that I tend to skip for breakfast (or any other meal for that matter). The tent is slightly wider than my sleeping mattress, and nearly double my height. This seemingly excessive length allows me to store my backpack, hiking boots and other voluminous stuff within easy reach behind my head. Both the tent's tail and head ends have a loop, allowing me to stabilise it lengthwise. I don't have any tent pegs with me (weight obsession, again), but a stick or a large stone will do just fine. These are usually available in abundant quantity throughout the Alps, though not necessarily in the same place. The tent can be ventilated from head to toe (and vice versa) by having the tail and head end loops a little off the ground. About ten to twenty centimetres, or more more if it isn't raining or too windy. Often being too lazy (a synonym for efficient) to prepare two sticks, I will simply fold the tent's head end underneath my backpack. This stabilises the tent better than by using the loop, but completely blocks the ventilation entrance. Fortunately, or rather by design, the sides of the tent can be raised for ventilation as well.
This characteristic also comes in handy for admiring the surroundings, without having to raise my head in order to peek out of a window or having to hear that dreaded zipper sound. Once I was woken by the noise of two deer having a territorial argument next to my tent, at four o'clock in the morning. Seeing wild deer so close, is a special experience. Their arguments sort of being shouted in my ears, made it even more impressive. I silently raised one side of the tent. Just a tiny bit, in order to have a unobtrusive observation of the event. A far nicer gesture than bluntly announcing my interest with the built in zipper or Velcro alarm that ordinary tents are equipped with, and thus scaring them away. Even though I am sleeping in a tent, which is a significant change from my practice so far, it still feels like I am sleeping in the open air. Especially when I (slightly) raise the side(s).
The tent is supported by three arcs created by fibreglass rods. These rods slide into tunnels that are sewn onto the fabric. The rods' ends are connected by straps that pass underneath my mattress, which doubles as a groundsheet in order to save weight, giving the tent lateral stability. These straps have holes at regular intervals, to accommodate a rod's end. This allows me to tune the tent's width and height within seconds to the conditions or desire of the moment. For example, I could lower the roof in windy conditions, or raise it to have maximum headroom and ventilation during a rain shower. All this without having to leave the comfort of my tent. Each arc tunnel ends in a loop on both sides, allowing the tent to be anchored to the ground in windy conditions. Or to tie it to a tree or wall, using it as a tarp. The latter usage also explains the sloppy appearance of the tent (especially near the ends), which in fact is nothing more than a large rectangular tarp being forced into a long round tunnel shape. This slight geometric incompatibility creates some wrinkling compromises here and there in the process. I don't care. I prefer functionality over looks, especially when looks don't matter.
The tent's package volume, including the three flexible rods, is about 25x25x0,8 cm. It weighs over 400 gram for the moment, since I am using a rather solid lightweight fabric. The problem with most of the lightweight materials is that these normally won't last that long when really used in practice, despite all the advertisement saying so. It is not uncommon for lightweight equipment to fall apart after a few weeks or a season. It is not that I am abusing it, I am just using it a lot. Probably a bit more than the average buyer, to be honest. Which explains the difference between the sentiment conveyed by the advertisements and the problems I encounter in practice. I therefore preferred to use a rather heavy lightweight fabric of 64 gram per square meter, resulting in the tent exceeding my original weight requirement. This decision was facilitated by the fabrics green colour. The lighter fabrics were only available in screaming colours that strongly contrasted with nature. Exactly the opposite of what I am trying to achieve. Cutting off a metre or so will bring my tent under 400 gram, while still having adequate space I guess. Using 30 gram fabric could bring the weight of this tent down to 200 gram or less. That sounds tempting, doesn't it? If such a lightweight tent wouldn't last that long, then maybe I could consider this an opportunity to make a new one every year, rather than as a quality problem.
The current tent is a prototype that still needs a few small but important additional details. The main issue will probably be ventilation. It would have been nice to have breathable fabric. The durability, impermeability, and colour of the fabrics found however, did not match my quality wishes. The current prototype has been created in a few days and it is far from perfect, but for the moment it is doing fine. Besides that, practice tend to be a better tool than the drawing board. Weeks needed to design the perfect tent, only to find out on its first day out that I overlooked something crucial, are better spent flying and hiking with a not so perfect tent that will be honed by practice, by nature.