The Royal Marine Rig by Mike

This is a tactical way to use a USGI surplus poncho as a shelter in the field. This method was taught to my old regiment by a Major from the British Royal Marine Commandos, hence the name I have given it. It is easy to set up, takes up almost no space in your pack, and (most importantly) can be taken down in seconds. All you need is a USGI poncho and about 50 feet of paracord.

First, cut the paracord into two roughly equal lengths. Take one of them and tie the ends together with a square knot. Then, pinch the part furthest from the knot and attach it to the CENTER grommet on one end of the poncho, as shown in the picture below.

Next, grab the two strands of cord and tie a series of overhand knots about one hand width apart. Do this for the entire length of the loop you just made. It should look like this;

Repeat the entire procedure on the opposite side of the tarp. Now you have finished the prep work, and you can begin making your shelter.
Select a suitable spot between two small trees about 10-15 feet long. First, remove any sticks, rocks, or pine cones that will jab you in the back when you lie down. You may choose to add a layer of leaves or pine needles for additional cushioning/insulation from the ground. When this is done, take one of the lengths of knotted paracord on your poncho and wrap it around the first tree. You can secure the cord by taking a knot from the running end and tucking it in between the cords on a portion of the standing end, as shown in the pic below.
Note that I did not pull the entire length of cord through, just the one knot. This is important for later. Maintain tension on the cord and it will hold securely. Move to the second tree and do the same thing with the opposite end of the poncho. Now it should look something like this;

You will now want to adjust the height on both ends to however tall you want your shelter to be. I recommend as low as possible while still allowing for you to crawl inside and lie down without touching the tarp. This way you keep a low profile, making your shelter harder to spot.
Once you have the desired height, stake down the corners using the grommets on the poncho. You can use actual stakes if you want, but they’re not necessary as long as there are plenty of twigs lying around. I just snap off the length I want, and push it into the ground at enough of an angle to securely hold the corner down.

If it is exceptionally windy, you may choose to stake down the middle of the sides as well. The finished shelter looks like this;
Once finished, you should have enough room underneath for yourself and your gear. If your poncho has a hood like mine, make sure it is on the outside of your shelter and not dangling inside. All together, setup takes no more than 2-3 minutes if you have the paracord already prepped. Taking the shelter down is even quicker. Remember how you weren’t supposed to pull the entire cord through the loop during setup? To take down the tarp, just pull on the loose end to pop the knot back through.
You can now scoop up the poncho, quickly fold/roll it up, and loop the paracord around it to wrap it up nice and compact.
Teardown takes mere seconds. Throw it into your pack and you’re ready to move.

A few notes on tactical shelters. This is not intended to be a semi-permanent camping setup (though you could use it for that), this is for when you must spend the night in the field and there is a chance of rain. Only put up your shelter when you are about to lie down under it and put it away as soon as you are done. As quickly as this can be taken down, you should always keep your gear as packed up as possible at all times so that you can quickly grab it and go when you need to. Keep your poncho somewhere on the outside of your pack so that you don’t have to dig around for it when setting up in the dark (I keep mine wrapped around my sleeping pad on the side of my pack). When you are lying down in your shelter, position yourself so that your head is facing outward from your position (towards where an enemy attack would come from) and keep your rifle inside with you, muzzle also pointed outwards. This way, if your OP comes under fire while you sleep, you can grab your rifle and engage the enemy without getting up and exposing yourself.
Stay frosty, gents. Train hard and shoot straight.
-Mike