where somone hits someone else in the area above the kneecap
on the side of the left leg with their own knee. why? because its bloody funny (only if it works)!! the consequense of this will be the other person hopping on one leg shouting swear words,while u and ur m8s r laghing like hell. also some advice: always give a grandad when the other person is noot expecting and make sure u r
standing up when doing it. there are adaptions of
the grandad like a 'running grandad', the 'spinny' and a 'flying grandad'.