I saw this concept at a store, as a commercially made product. I thought it was great, but it could use a few modifications, then I saw the price of $40, and decided I could definitely make one that was about 1/5 the cost, and more usable, so here it is.

The concept is simple, a highly portable strap that goes around your legs and back as you sit, and provides back support, but can be thrown in your backpack/purse/pocket and carried around. I think it's brilliant! You can use one of these on the floor, on the ground, on a couch or chair, or anywhere else where you want a little more back support. The only downside is that my rear end gets a little sore from this. I think I will add to it by taking a small piece of closed cell foam around as a seat cushion.

Step 1: Materials

Materials:

2" Webbing: 2-2.5 yards
1/8" or 3/16" Shock cord: 6-8"
2" "Loop Loc": 1
2" Tri-glide: 1
Optional- Small piece of leather or cloth

Supplies:
Needle and Thread
Sewing Machine is nice
Something to cut webbing and fabric/leather

I used Tubular Nylon Webbing, I would recommend against that, because it is significantly bulkier and heavier. I'd suggest either polypropylene, or if that's not available you could use flat nylon. Really you could use anything. This could be done with seat belt webbing and a buckle from an old car and look much cooler than mine.

You could also use a variety of other options on the buckles, I just wanted something that could be adjusted and this stuff was handy. Also for mine I used 1/4" shock cord, I would recommend using lighter weight shock cord (actually the shock cord is optional).

All of these materials can be had from a variety of retailers, some of my favorites online are: Outdoor Wilderness Fabrics and The Rainshed.

I apologize for not having pictures of the whole process. Please let me know if there are any other pictures that would be helpful!

Step 2: Sew the Loop Loc to One End of the Webbing

Just fold the end of the webbing through the loop loc (white plastic piece) and stitch it down. I Stitched back and forth several times. sorry I don't have a picture of just this step.

Step 3: Stitch Shock Cord Onto Webbing

Now you need to fold your shock cord in half, and stitch the two ends just behind the ladder lock so that it pokes out over the ladder lock. I used a stitching awl for this, but a heavy needle would probably work.

Step 4: Make a Cover (if You Want One)

If you want a little cover to hide the stitching on your shock cord, then choose your material, cut a rectangle approximately 4.5" x 2". Fold it in half and sew down one edge so you have a "tube". Slide it over the part of the webbing you want to cover, and then stitch down one side through the webbing to anchor it.

Now you're done stitching!

(BTW, I used lime green deer hide for my "cover" It came from an auction so I'm afraid I've got no idea where you can get some!)

Step 5: Feed the Webbing Through the Triglide

Bring the other end of your webbing through the triglide, then through the loop loc, then back through the triglide. This should complete your seat!

Step 6: Enjoy!

There are many ways to use this seat(less), You can use it with your legs up higher, or crossed, or even in the lotus position (though that requires a fairly long strap). Put your back strap on your lower back for lumbar support, or up higher, it's quite versatile!

Incidentally, if you happen to have a scrap of webbing lying around, you can make a non adjustable one by just tying a Water Knot in it as shown in the last couple pictures.

Step 7: Add Padding!

Several people have expressed concerns about pressure on kidneys, discomfort, etc. so I tried a couple padding options that occurred to me. The first is a small section of a closed cell foam sleeping pad that is ~20"x13". This is just long enough to go under my bottom, and then under the strap when it's down low. It did a really good job of spreading the pressure of the strap. The second idea was to use this with an actual sleeping pad, in a manner similar to the therm-a-rest kit for turning your sleeping pad into a stadium chair. This was also comfortable, and with the addition of some protection for your sleeping pad could be an excellent method while backpacking. I hope this helps waylay any concerns about danger, and also contribute to your comfort of course :)