Tegatana is a typical technique which comes from Samurai tradition but most Aikido teachers do not know how to create it.
You must create form of your arm and hand which is very strong and stable.
First put your elbow on a table so that it does not move.
Then you must see that your hand can move either toward the little finger or thumb.
So move you hand maximum towards your thumb.
then turn the arm without moving the elbow.
The arm is a part of your body between the elbow and the wrist.
Now you have a correct form of Tegatana.
25. March 2020.