The most common type of joint in the human body is the diarthrodial joint -- knuckles and shoulders are examples -- in which two bones come together in a capsule.
We've recently been able to use some new technology through MRI imaging to see for the first time what is actually happening inside the joint when someone pops or cracks their knuckles.
STEP 1 Wrap the string around the base of your ring finger. Pull the string so that it is snug, but not too tight. Keep the string loose enough to snugly slip over your knuckles.
And you missed every now and then too, and you'd get a hit on the knuckles or something, and that always left a mark, but getting to swing a lightsaber is pretty awesome.