Keito-uke (literally: “chicken-head block”), the thumbknuckle block, can be thought of as a variant of the ridgehand block, or of chūdan uke. Thumbknuckle blocks use a modified fist, where the thumb presses down on the side of the index finger, as demonstrated in the photo to the right. Thumbknuckle blocks hook the opponent’s wrist with the back of your thumb, so you can off-balance them with the reciprocal action of your counterattack. While this hooking motion is not as solid and secure as the grasping block’s Unbreakable Circle, thumbknuckle blocks are faster to apply.
[photo of a thumb kuckle bloc. ]
[video of thumbkuckle block,s fast and slow, from front as side. ]