Dummy door knobs and levers are often confused with the other function called passage. It's mostly when someone is looking for a passage door knob which is a door knob or lever with no lock but it has a mechanism and it does function, and they mistakenly order a double or single dummy. Dummy door knobs and levers are non functioning and are mounted straight to the door. Most of these can not have a bore hole in the door or it will not work (the Sure-Loc Juneau Dummy lever set at one time did require a bore hole and it basically installed just like a regular passage but it didn't have the mechanism to hold the door in place. I don't know for sure, but maybe you can still find dummy sets still out there like that). So let me start again, most likely when you order a dummy or a dummy set (double dummy) they are mounted to the door, which means you most likely can't have a hole or you won't have any way of screwing the door knob onto the door. What types of dummies are there? Single Dummy: A single dummy is one single non functioning door knob or lever that is mounted to the front of the door. Remember these will not mount to door that have a bore hole. Double Dummy: A double dummy set comes with two non functioning door knobs/levers. These are great to purchase if you have double closet doors (which are very popular) where all you do is pull them open. You can mount each door knob on the front of each door. Or you can mount these back to back if you want door knobs on both sides of a door, the Sure-Loc door knobs and levers require a spindle for it to be possible to mount them back to back, available upon request.