Projective Hand
Although our right hand is our dominant hand, our left, with regards to magic and such, is our projective hand, or, power hand. It also happens to be the hand that has my personal sigil tattooed on the back of it. Looked into how to determining this (besides the fact that it just feels right), and came upon this quick little test:
Simply sit comfortably and fold your hands together on your lap so that your thumbs cross over each other. The hand that is attached to the thumb that sits naturally on top of your other thumb is your power hand, or your projective hand.
Done and done, and what do you know, it was the left for me. I then tried it the other way around and it just felt weird.

















