I used shorter bolts than Bob provided because I have stacking cages. I predrilled by laying the panel on top of the cage and drilling through the bolt holes, and drilled a hole in the back where the cord lined up to feed the cord through about 1/2 from the cage top. Then I dropped the bolt through a washer then through the holes I drilled. It helps to have 2 people for a larger cage, one to hold the panel in place while you secure the nuts. But a small cage would be easy enough to flip upside down to make fitting the panel over the bolts easier. I secured the panel with lock washers and an acorn nut (you can see it pretty clearly in the foreground of the picture I posted). The bolts I purchased were the depth of the panel plus the thickness of the cage, with an extra 1/4 inch for the lockwasher and nut.
For the probe I drilled another hole about half way down the cage wall under the panel. I fed the probe through the whole, then it is secured in place with a cable strap and small screw. My cage walls are 1/4 thick, but if your cage is thinner like my Barr’s cage, you could either drill 2 holes side by side and secure with a zip tie or use a small bolt and nut through the wall with the cable strap. The small cable straps I got were from Home Depot in the wiring section...basically used for securing lengths of cable or wires to a wall. I guess you could also just leave it hanging loose, just tape the extra cord on the outside to keep it from shifting positions.