I think and am just guessing here is that she gives him tasks to do as part of an obstacle course - like climbing a ladder and then doing something at the top. Or she has him lay on his stomach and do a puzzle or lay on some kind of scooter that he uses his arms for. So possibly, the stacker was just something she had for that - but yeah, I was kind of bewildered too - but then worried!!! We probably should get the vision testing done to see if there is a legitimate issue.