Another type of throw in ultimate frisbee is called the thumber. It’s called a thumber because the disc is held between the thumb and the rest of the fingers and the spin on the disc is generated when you throw the disc off your thumb. As you can see by the grip in Main Thumber Grip, the thumb goes along the inside of the rim. There are variations on where the fingers go as shown in Squanto Grip and Split Finger Grip.
I almost never throw a thumber because it’s not similar to any of the other grips (a hammer or scoober uses the forehand grip so they are easy to work into your fakes) so it’s difficult to throw a thumber quickly without changing your grip or catching the disc in the thumber grip.
I like throwing a thumber when I want to get the throw to my receiver quickly and when I need it to have a bit of height since there people in between me and my receiver. When you practice throwing a thumber, practice different release heights. If you release with a straight arm at the top of your head, the disc will start high (like a hammer) and then flatten out as it flies through the air. You can also develop a lower thumber which you will release just above your shoulder which will fly quite flat the whole time. This is good for when you have a receiver who is wide open and you’ve caught the disc in the thumber grip and you want to get the throw off quickly.
A great way to practice the thumber I’ve found is to practice throwing it into a basketball net. By practicing this, you will develop your range and accuracy. And most importantly, you can experiment and learn how much the disc moves as it turns over so you will know how far to the left or right of your receiver you need to aim in order to have the disc be catchable.
As much I think it’s good to know how to throw a thumber, I think it’s much more important to throw your forehand and backhand more regularly since those will be your main throws in a game. But remember, the key to getting better at throwing is practice, practice, practice.
For more, check out the video that illustrates how to throw a thumber: https://ultimaterob.com/2009/12/30/how-to-throw-a-thumber-squanto/