Babinski
Stroking the sole of the foot with a key (blunt instrument), from the heel along the lateral edge and then across the ball of the foot medially.
Normal response= Toes down.
Extensor Plantar response= Great toe up with fanning of the other toes.

Variants
Abnormal response consists in dorsiflexion of the great toe (with different sites of stimulation).

Chaddock: Lateral edge of the foot from the heel to the toes just above the sole.

Oppenheim: Firmly pressing down on the shin with the knuckles from the knee to the ankle.

Gordon: Squeeze the calf firmly.