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Step Forward with your Right leg into Back Stance (Kokutsu Dachi) Knife hand Block (Shuto Uke)

Feet Position on Diagram Facing Screen

Bring your Right foot straight in to your Left foot.  Carry it on past your Left foot  in a straight line towards the 12 o'clock direction. 
Your heels should finish in a straight line.

As you bring your feet together, bring your Right hand up to your Left shoulder and stretch your left hand in the direction you will be finishing the block (straight ahead), palm down.
As you step forward,  push your Left arm and hip forward, keeping your Right hand at your shoulder until just before your feet land in the correct position 
Make sure you  step in a straight line keeping most of your body weight over your back leg - step to the 12  o'clock position
As your Right foot touches the finish position, bring your Right hand forward quickly from your shoulder to finish with your finger tips in line with your shoulder and your arm bent to 90 degrees.  At the same time bring your Left hand quickly back to just below your solar plexus - hand open - palm facing upward
Your elbow should be no higher than your lower ribs
Pull your rear shoulder back, so your chest and rear shoulder are hidden from someone facing you
Make sure your front leg is slightly bent, toes pointing forward, and your back leg is bent, knee pointing slightly backwards
Most of your body weight should be over your back leg.  You should be able to lift your front leg to kick without pulling your body weight backwards
Breathe out completely and tense all your body muscles for a brief moment on the completion of the move