I'm not gonna say that I invented this technique, because it's almost definitely already out there somewhere, but I did come up with it on my own. I'm making a chapstick holder keychain for my mom, and since it buttons closed with a flap, I wanted to put a loop for the keychain in the middle of the flap. I figured it would be more secure if I could somehow crochet it into the flap while I was making it rather than sewing it on or just using a strand of yarn. So this is what I came up with:

1. Work normally to where you want the loop to start. 

2. Chain however many stitches you would need to connect it to the desired stitch, plus a few. I skipped over four stitches, and my chain was six stitches long.

3. Connect the chain back to the desired stitch like you would normally. Finish the row.

4. Crochet normally until you get to the stitch where the chain is connected. For me, this was stitch 3. Crochet that stitch normally.

5. Use a stitch that is double the height of the stitches that make up the rest of the work. Since mine was done using single crochet, I should have done the gap with double crochet, but I mixed their heights up in my head and used half double instead. To pull through, feed the working yarn through the chained loop first, so it doesn't go over the top of the chained loop and make it useless. 

6. Pull the working yarn back to its normal position at the back of the work. Repeat for all the skipped stitches.

7. Finish the rest of the row regularly, with the stitch that's used for the main body of the work.

That's it! It's got pretty niche use cases, since I don't think it would work across multiple rows like at the center of a project. I'm proud of myself regardless. I've only been crocheting for about a year, so if I missed something really obvious, that's why.

I tried a technique that I came up with