This trick is one of my favorites.  Kids ask me to do this one all the time.

What you’ll need: Your hands.

How to do the Pull off Your Thumb Trick:

• Present the back of your left hand to your audience, with your thumb up.
• Take your first finger and thumb of your right hand and pinch your thumb of your left hand at the knuckle.
• Wiggle the left thumb a little and say, “ The first thing you have to do is get a really tight grip.”  Then you need to pretend you are going to really pull hard on that thumb by getting a better grip.  When you go for the better grip is when you do “the move”.
• While still keeping the back of your left hand towards the audience, you are going to bend your left thumb down and bend your right thumb to the right and you are going to put them together to make a “thumb” that your audience sees at the top of your left hand.  There will be a line between the two half thumbs where the knuckles touch.  You will need to cover the gap with the end of your first finger of your right hand.
• You can slowly slide your right hand and thumb, with finger cover, along the top of your left hand about 2 inches to the right and then slide it back quickly.  Be sure and groan because it hurts to pull off your thumb.

Practice in front of a mirror to see what your audience sees.