Autoblock tip: make a twist to fine-tune friction
When you tie an autoblock / thirdhand rappel back up, sometimes you may find that your hitch has either too much or not enough friction. Here's a trick that can help with that.
Remove one of the wraps, and then twist one strand of your friction hitch several times. This makes the remaining wraps constrict a bit around the rope. You can think of this is the equivalent of a half of a wrap, which can give you just the right amount of friction.
Here's a short video from IFMGA guide Ian Nicholson showing how it's done. Check out Ian's books, highly recommended!