This is a great tool for strengthening the hand in general, but specifically for helping develop hand arches and strengthen the base of the thumb for opposition to the index finger (very important for optimal pencil grasp and mechanics). I use it most for children four to eight years old, but some older kids love them too.


Here's what you do...
Take an old tennisball and CAREFULLY (I can't tell you how many times I have almost cut my palm doing this) cut a slit across the ball with an exacto knife or similar sharp blade.  The longer you cut the line, the less resistive (easier to squeeze) the ball will be. Try it out and cut it until it is about as difficult as you want it. Now put on eyes, hair, whatever. You can just use a permanent marker, or fabric paint, yarn or feather for hair, whatever. Sometimes I cut a little X in the top and then push knotted yarn through with a darning needle to make hair. If you let the child draw on the face, they are often more invested in the toy.

Now place your thumb on one end of the mouth and your middle finger on the other end and squeeze. It should open the mouth like a changepurse. You can make your new friend talk, eat, bite...  Here is the printed page I give to kids to take home with their new tennis ball friend:

Care and Feeding of Tennis Ball Heads Congratulations!  You are the proud new owner of your own tennis ball head!  Here is how to take care of him or her: Tennis ball heads are almost always hungry.  In order to feed your tennis ball, you need to help him/her open his/her mouth.  Put your thumb on one end of the mouth, and your fingers on the other end.  Now squeeze.  Tennis ball heads like to eat almost anything that will fit in their mouths.  They like dried beans or pasta, small rocks, coins, dice, cotton balls, paper clips, marbles, bits of wood, small game pieces, and fingers.  They do NOT like human food, including peanut butter, ice cream, macaroni and cheese, or anything else soft.  You should try to feed your tennis ball at least once a day. Tennis ball heads can help you with addition and subtractions.  For example, suppose a tennis ball eats 3 beans.  He is still hungry, so he eats 3 more beans.  If you were curious about what 3 + 3 =    you could find out by making him spit out all those beans and counting them. Tennis ball heads can also play spelling games with you.  If you let your tennis ball eat small pieces of paper with letters on them, you are ready to begin.  Each player take turns picking out letters.  The first person who can make a word with his or her letters wins! Tennis ball heads are also very helpful at picking up spills of small objects, and they like to attach themselves to various household items and “hang out.”  See if yours likes to bite curtains, the backs of chairs, or doorknobs.  Family members’ body parts are not allowed, but you may be able to attach your tennis ball head to a sleeve or collar.  Make a fashion statement!  Start a trend! In any case, enjoy your tennis ball head.  They are pretty easy-going and don’t demand much attention.  Just don’t forget to feed them.  You wouldn’t want to see a ravenous tennis ball head…!