I tied this lanyard last year, with a leftover scrap of neon pink paracord, thus the black and white photos, lol, and stuck it in a drawer. At the time, I thought no one would be interested in it, but digging it back out, someone may find it useful and be able modify it to their own use. Perhaps running their belt though the loop, keeping the lanyard shortened for pocket carry, then extend the lanyard while still attached to the belt for use, with the swivel clip/snap hook allowing quick release of an item if preferred, etc...
Here's a YouTube video link for a short demonstration of the lanyard.
I may add a tutorial/walk through for making this particular lanyard later. But for a brief description: this one was made with about 4 feet of paracord, tying one Celtic Button Knot, making a loop, tying another Celtic Button Knot around the loop strand, then running the cord through the first Celtic Button Knot, tighten them up, and tying a Scaffold Knot(Multiple Overhand Sliding Knot) at the end of the cord to finish, where it can be attached directly to an item, or swivel clip, key ring, carabiner, and so on.
It may sound a little confusing, and hard for me to explain, but the Celtic Button Knots are tied on opposite sides of the loop, before the cords go through the center of them.
Shown attached to the lanyard is a blue alox Victorinox Farmer Swiss Army Knife, a gift from friend SwissBianco that he gave me in 2007.
You can use other single strand knots, like the multiple overhand knot(example comes from Peter Owen's 'The Book of Decorative Knots'), tied loosely at one end of a length of cord, make a loop, tie another knot around the cord back toward the first knot, taking the cord through the first knot, tighten them up, finish with a scaffold knot, slip knot, etc.. to complete.
The one shown with the flashlight was done with about 4 feet of foliage green paracord, and the only problem with this knot, is that it's tightened around the sliding cord when pulled in either direction, so it can be harder to adjust compared with the Celtic Button knot.
A photo walk-through for tying this type of lanyard can be seen with photos I have stored on xanga(now gone, buggers).
Once you know how to tie the Celtic Button Knot and the Scaffold/Multiple Overhand Sliding Knot, you can follow this sequence of photos to tie the lanyard. I used a four foot length of paracord, but you can use more or less to make one to your own preferred longer or shorter length lanyard.
When in the shortened length, the Celtic Button Knot on the loop side can be moved along the length of cord that it's tied on, by moving slack from either side of the knot through it, and that will change the wrist loop size. Of course the simple design is open to variation, modification, and improvement, so experiment with it. I hope folks find it useful.
Photos recovered, thanks to the Wayback Machine.
The way I sometimes tie a lanyard knot to finish at an attachment/swivel clip, also can slide, but I just haven't used them that way. With the cord looped around the attachment and then tying the lanyard knot with the cord in the center, the knot can be moved up/down the cord to the last knot tied, example seen here at the swivel clip. I just found the double loops of slack to be in the way, but someone might pursue trying something out with it...