Lay out a jar lid on the top of the feeder. Locate the center of it approximately 2 /2" from the closed end of the feeder and centered side to side. Mark around the lid and drill a 3/4" hole inside the mark. I used a step drill bit. I then took a sheet metal shears and carefully cut a spiral shape to the line. I did this in order to get a smoother cut.I also found by cutting small increments, the cut came out smoother. Take a half round file to smooth up the cut edge. Keep checking the fit of the lid until it fits freely inside the hole and does not fall through. A Dremel can also be used to smooth up the hole. A hole saw can also be used to cut the hole if you have one the correct size. At this time make sure all sharp edges are filed and then smoothed with Scotch Brite.