I will spare the details, and simply say that this mole trap works.  However, when installing you may have to experiment and find the correct height.  The instructions do leave a little to be desired in this regard.  After some experimenting, I was able to find the perfect height to install.  In my instance, the flapper was positioned just below the little mound of dirt described.  The instructions left me with a trap stuck way too far into the dirt.