You need to buy an original Acme(tm) Permanent Marker. They're no longer sold at office supply stores, but you may be able to get one on eBay, or at a smaller mom-and-pop stationery store.Anyway, once you've got your Acme Marker, just draw an outline of the hole on your wall, whatever size you want. Make sure you choose a wall directly across from a door, or it won't work quite right. Color in the hole carefully: stay within the outline, and make sure the region is completely filled (no little gaps where you missed a spot).You can verify the operation of the hole by stepping outside the room, and running as fast as you can through the door and toward the wall. If you can get someone to take pictures, please post them here!