Materials: 2 jump rings,chain,2 post style earrings,2 pins, pliers,hot glue gun, small fabric or ribbon(optional).
Step 1 - Using the pliers take the pointy part off of the back of the earring. On one earring I managed to get it all the way off. On the second there was a little stub left,that's okay. I placed a small dot of hot glue and a tiny piece of fabric over it so it didn't hurt me or my cardigan. You can see it better in the next picture. Step 2 - Glue the pin to the back of the earring. I don't like the way hot glue looks so I covered it with a small strip of fabric. Step 3- Attach a jump ring to one end of your chain. Then place it on the pin bar. It will move around.
Step 4- In front of a mirror determine how much chain you want. I used about 10 inches. Then cut you chain and attach a jump ring. Place the other end on your pin and wear.
This isn't a traditional sweater guard because the chain is removable. That is better because you could make a ton of earring pin and just switch the chain. You could also make a few kinds of chains and maybe add beads. You could also use an old necklace as your chain.
I hope you try this out. If you have any question you can leave them in the comments.