A match is placed in a match box and then closed, when opened the match has doubled and there are now two matches in the box.
WHAT YOU WILL NEED:
Before the trick place one of the matches between the lid of the matchbox and the tray which is pulled about three quarters of the way out. Now show your spectator the empty matchbox and put one match in then close the matchbox. When you open it again there should be two matches inside.
When you close he matchbox, cover the back so the match doesn't pop out.
When you show the empty matchbox at the start of the trick, tilt it towards the spectator so they cant see the match hiding inside.