I was perusing a German knife shop online, looking for a new pocket knife, when I saw a section of the shop, devoted to 'lanyards'. Along with the usual knotted and looped lanyards, there were 'monkey fists'. A little tied ball with a cord, for tying to your knife (especially smaller knives) for easier removal from your pocket and for decoration. I was aware that it was common for lanyards to be added to pocket knives- I follow The Items We Carry group on Flickr, which has plenty of photos of lanyard adorned pocket knives.
I researched a bit further and found most lanyards are tied with 550 Paracord, which is parachute cord with a breaking strength of 550lbs. I also discovered that tying monkey fists and other lanyards was quite straightforward, and looked like fun.
I found a UK shop on eBay which sold different coloured Paracord, and I bought nearly 100 foot of different colours, for the princely sum of eight pounds (including shipping). I have been making them ever since I got the Paracord and once you get the hang of tying the knots, it's really a lot of fun making monkey fists! I need to start giving them away, so I have an excuse to make more.