Though at Comstock Custom Cage we do make and sell single door traps, the primary objective in this endeavor is to provide superior equipment along with the most effective methods that offer more options and versatility, which simply put, is a double door trap over a single door trap, something that should not be difficult to grasp.  Those using single door traps like having a second bait door in order to make placing or changing bait easier and faster, so why no make the bait door a working door.  The double door trap has the option of usage as a bait door as an added byproduct, while at the same time is a functioning door to be used in a pass through situation.

Single door traps are  a one dimensional tool, limited to taking animals coming from one direction period, which is exactly half of what a double door will do.  A double door trap, open at both ends, gives the approaching animal a degree of confidence not felt in a single door trap.  Instead of a dead end in a single door trap with wire at the far end, the animal can see through the trap, removing the feeling of confinement.   
Double door traps not only have the option of being used with bait with either one or both doors open, but can be used in trail sets where animals are simply moving from one location to another, often following structure, a fence, a wall, or terrain, a ditch, a ridge.  Placed at den locations, double door traps shine simply because it is not always possible to determine if the resident is in or out.  No sense guessing with a single door trap, while potentially guessing incorrectly about the direction from which the animal is coming and instead of catching an animal coming from a den actually block one from returning.  Just place the double door trap and take any animal either coming from or entering the den.