One of the finest investments one can make towards the Survival Kit, indeed one of the most important pieces of equipment that should be a part of all Survival Kits, is a tarp sheet.
A tarp sheet is small, lightweight and can be used in many different ways. A waterproof, nylon tarp sheet is best for survival purposes compared to a canvas one. A canvas tarp sheet may last longer and be a lot more waterproof and weather resistant, but when push comes to shove, you want something that is easily accessible and portable, yet lending itself to everything that a canvas tarp sheet can accomplish. A nylon tarp sheet, eight feet square, can quickly and easily be transformed into a temporary shelter, keeping you protected from the wind, rain, heat, sleet, dust, etc.
Shelter is your primary concern in the wilderness, particularly when you are lost, fatigued, possibly panicking. A nylon tarp sheet, eight or ten feet square can pack into a really small volume, enabling you to pack it in your Survival Kit certainly and even your PSK, so that it is always with you.
A tarp sheet can be used to construct shelters of many different configurations. The exact configuration depends on the terrain and the weather. It can be open on a couple of sides in warmer weather to allow for ventilation or locked in from all sides to prevent the draft of wind from making you uncomfortably cold. You can decided to fold over one side to get a ground sheet to sleep on. It can be constructed like a tepee, with or without a door. A larger tarp sheet can also accommodate a small fire inside the shelter as long as there is enough ventilation for the smoke to dissipate. If the ground is wet or sloping, you can rig up a hammock too.
Apart from shelter, a tarp sheet is an excellent container to collect rain water. And if it is clean, you may not even need to disinfect the collected rain water. But you are probably better off disinfecting water in any case ... just to be doubly sure. There's no point in taking chances with a bad tummy!
When purchasing a tarp sheet, try and buy one that has a distinctive colour, something that will stand out from the background of whatever terrain you plan to be in.
A green tarp sheet in a jungle will be worthless as a signalling device. An orange one will stand out like a beacon, seen from many miles away. Use your tarp sheet as a signalling device if ever you fall into a situation where you have to signal for help and rescue.
Another use of a tarp sheet is for fishing in shallow waters. Lay the tarp sheet on the stream bed. If you are alone, stake two corners, a little above the surface of the water and lay the other two corners on the bed itself. Wait for some time and allow the fish to swim in the area of water above the tarp sheet. When you see enough fish floating above your tarp sheet, pull the two corners that were below the surface of the water, up and out of the water. All the fish will get trapped in the bowl formed by the tarp sheet. Gather the corners together and bring the tarp sheet to shore. You should be eating well.
Strips cut from the tarp sheet can be used for bandaging, lashing, fishing line, as cordage, even as a fire accelerant. Dropping a piece of tarp sheet on your fire will give off dark smoke, making the signal fire more visible.