This effect is the most effective in a very small haunted house where you want to slow them down and make it seem like the haunted house takes longer to get through. In a plain hallway are mounted several doors. Some open it, some open out, some have hinges on the left and some have hinges on the right. This one will confuse them every time. You can also put the hinges on the wrong side of the door (the same side as the knob). That really messes em up!!! This effect is very effective in complete darkness. It's a great effect, but it does reduce throughput.