Here's the effect: girl gets in the box and doors are closed. Spikes are lit on fire (we didn't light them all in our studio), and spikes are pushed through the box while the person's hand is sticking out through the front door..........
Doors are removed and the person has vanished! After they re-appear, a second person appears!
This one was actually built to hold 2 men!
This one was built larger, to hold one guy and two girls. It also featured getaway steps so the performer could vanish, and appear at the back of the room.