This is a new version on an old puzzle. Invented by Sam Loyd 1841-1911. The puzzle is placed on a buttonhole and seems impossible to remove. This is where the term buttonholed (to get someone's attention) came from.
Step 1: Materials and Tools
I used para cord and some copper pipe 1/4 O.D. x 5/32 I.D.
The main thing is to pick something small enough to fit thru a buttonhole.
Something to cut the para cord. A hot knife would work best, I used the knife on the Multi-tool.
Something to fuse the ends of the para cord. I used a lighter and a candle.
Something to cut the pipe. A pipe cutter or hacksaw. I used the saw on the Multi-tool.
Something to smooth the pipe, after cutting. I used the file on the Mulit-tool and fine sandpaper.
Something to crimp (Smash) the pipe. Pliers, hammer, press, clamp whatever, not your teeth.
Step 2: Cut the pipe
You will need to cut the pipe 2 inches long. If you get your pipe from the local plumbing supply store, tell them you need a few two inch long pieces of 1/4 inch pipe. They will think you are crazy and probably not charge you for it. Remember to make an extra puzzle to give to the guy at the plumbing store, even if he does charge you. Karma is something that goes around and good karma travels faster.
Step 3: Smooth edges of pipe
Smooth the outside and inside edges of the pipe. Use a file followed by sandpaper. If you role the sandpaper into a cone shape it gets the inside nicely. Note in the pictures that the puzzles are assembled, you should smooth both ends before assembling the puzzle, I just forgot to take pictures till after wards.
Step 4: Cut para cord
Cut the para cord to 5 inches long. I like to use a lit candle to cut and seal the cord at the same time. You could even cut the cord with another cord http://www.instructables.com/id/Cutting-cord-without-a-knife/ whatever works for you.