Remove from your pocket a matchbox and a toothpick. Push the toothpick straight through the center of the box, freely showing all sides with nothing to hide. Remove the toothpick and open the box. What they see is a solid brass block that entirely fills the box! The solid brass block can be examined. No skill required.
No sleight of hand! A self-working miracle!

Matchbox Block Mystery by Magic Makers (watch video)