Tate-shutō uchi is a bent-wrist version of the "karate chop", which is best suited for attacking the side of the neck, or the floating ribs. Tate-shutō starts out as a straight technique, exactly like a hasu-shutō. When the arm is halfway extended, pull the elbow in towards the centerline, and turn the hand palm-up. This will snap the wrist horizontally, for a powerful horizontal strike. Remember to chamber the opposite side hand for reciprocal action. For best results, let the strike pass through your centerline -- don’t strike the opponent’s neck, strike through it.
[videos of tate shutos, fast and slow from the front and from the side.]