Clackers were a popular fad during the 1970s. Over 42 million were produced by more than 1,600 companies by early 1971, according to Super70s.com. But these acrylic ball toys also proved to be dangerous, causing eye and head injuries when the balls stuck children or shattered. The FDA eventually forced the production of shatterproof clackers with nylon strings, but the hard balls still caused blunt force injuries. You can make toys at home, getting the same effect with balls that are safer and don't produce the annoying clacking noise that irritated parents in the 1970s.
Grip one tennis ball with your vise grips just enough that the tennis ball bends slightly.
Hammer your nail through the middle of the tennis ball, making sure to break through both sides. Remove the nail, and repeat with the second ball.
Push the crochet hook through the the holes in one of the tennis balls. Once through, thread the twine or string through the nail holes. Do the same thing to the other ball. The balls should be on opposite ends of the twine or string.
Tie a pony bead to each end of the twine or string to keep the balls from sliding off.
Find the midpoint on the twine or string between the two balls. This is where you will hold the string to play with the clacker. You can also attach a clothespin to the middle to serve as a handle.
Instruct your kids on how to play safely with clackers before handing the toy over. Use clackers outside to avoid damaging furniture or other household items.