I'll teach you to make a small, very inexpensive "Mummy's Finger". As you show it around, you make up some patter about how mummies never really die if their tomb is defiled. In another variation, you mention that your dad (or mom) works in an emergency room, and last night someone lost a finger in a horrible accident. You casually ask, "Ya wanna see it?"
Then you dare* one of the marks to touch the finger. Of course, just before he does, the finger moves!
The audience figures out it's your finger about 5 seconds later, laughs nervously, then starts dragging others over so they're not the only ones fooled. Best of all, the gadget is small enough to put in a backpack or coat pocket.
- Note that using a double-dog dare or triple dare is overkill and considered bad form.
Step 1: Gather Supplies
If the inside and outside of the box are not plain, you may want to either spray paint them or cover them with Contac paper (adhesive backed vinyl). For the mummy story, you want something that looks ornate, to distract the mark. For the ER story, it shouldn't look nice.
You'll also need craft or white glue and a large handful of cotton balls, or a 3" x 3" piece of felt, velvet or other thick cloth.
Finally, you can use a bit of color - a little red and gray water-based paint - to "age" the finger.
Step 2: Assemble the Box
Glue the cotton balls or cloth in the box. If using cloth, put it in loosely, with wrinkles or padding underneath. You want to camouflage the hole. I found that putting a drop of glue on the cotton ball worked better than smearing the inside of the with glue.
Step 3: The Result
The box will sit in the palm of your weak hand.
Place your index finger through the hole. Arrange the lining to hide the hole and base of your finger. Move your pointer finger towards the (missing) index finger to hide the gap. You can use the lid or lining to hide the pointer's gap. Practice opening the box and showing it around without moving your finger.
Work on your patter - find a story, tell it quickly, spring the surprise.