Hi Folks - I am trying to put an access opening in a gate door made of 6" wide plank fence board, so that the Chickens can access the front yard while the dogs stay in the back yard (thus the gate door remains locked). I am trying to figure out dimensions of the access, and where to place it (2' from ground, etc) so the chix can get thru, but not the dogs. Does anyone have any suggestions on this? My dogs are extremely crafty from an escape point of view, ie. they figure out how to open doors/gates/etc. Thanks!