Smart mice can figure these out!,
Bought one of these a year ago and after a couple of unsuccessful attempts I finally managed to catch a mouse.
First tip; set the mouse free a good distance away from your own house otherwise it will return time after time!
This Autumn I heard mice up in the attic again so looked out the trap. Once again they managed to get the food on a couple of occasions without springing the trap. On the third occasion I found to my amazement that the mouse had placed some loft insulation material round the door mechanism to stop it closing when the mouse went in for the food!
Again I eventually caught one but did not dispose of it immediately as I wanted to have some breakfast before going out of the house. When I went to get the trap to release the mouse while out for a walk, I discovered that the rodent had managed to release itself by gnawing a hole through the side of the trap!
Second tip; if you catch a mouse, release it a mile or two away from your house as soon as possible before it makes a big hole in your trap!