There are all kind of joins in knitting and in spinning too. All types share the goal of seamlessly or invisibly joining ends of fiber so you can continue with your project. In spinning it is important to achieve a smooth join so you do not end up with a bump in your finished yarn.
This is the way I have found that works for me when trying to create a smooth join while spinning. First, I have to stop treadling. That may seem like a very obvious step, but when I first started spinning it was very hard for me to do. I wanted to spin right through everything with no stops. So once I stop the wheel, I start by fluffing and fanning out the ends of my current piece of fiber; like in the photo above.
Then I take the new piece of fiber I want to join and fluff and fan that out to match the end of the first piece and lay them together in the hand I'm using to draft my fiber. I hold the ends together as one and then start the wheel and begin spinning and drafting.
If all goes well, you'll end up with a smooth invisible join in your spinning thread.