This trick is much harder to teach than the ones previously done a video for (spinning and walking on back legs), so apologies that the video is so long but it needs to be. You will need a lot of patience for this and may need to spend many training sessions on each step before moving on so that your rat can get used to the task at hand. If you move on too fast you will find that your rat will either ignore the glass altogether or at best put two front feet on it and just stare at the ball as though its impossible. If this happens just drop back a step and work with your rat to make that step more mastered before trying again.
Womble here has mastered the trick this far (although Im finding more and more that I can take this trick further and have big plans for the next few steps, so be creative), Whiskey is still a work-in-progress and I am using these exact steps so I know the process works.
Before each attempt its important to show the rat the treat and the ball so that it understands what is expected, I havent shown that often in this video (it was long enough already) but it is always done, just mostly off camera. Also, once your rats have gotten the hang of what is being asked of them (removing the ball) its worth taking the treat out from the ball, this tends to cause a distraction later on in the training rather than helping
If you get lucky you may find that your rat will pick up that it can jump on top of the glass early on and you can skip the frame steps but if your rat is just stretching on tip-toes to get the ball then dont push the rat too far in case they hurt themselves. When the ball starts to get out of reach find something that they climb to get to the top of the glass. Its an important part of the learning in most cases and even if you cant find anything like what I use in my video then perhaps try a small box or something that can give them that extra height so that the glass is fully vertical.