Thanks. I've seen that one and I agree it looks as though his arm holds back the next metal cube. Getting stuck sometimes in the process. There's also this video (see link below) where it looks as though his arm drags across the top of the next cube and then drops down behind it once he's all the way back into his starting position. I'm not sure either are the way it's supposed to work b/c the 770 was sold with either die-cast metal "boxes" or cubes or metal milk cans on square metal bases. His extended hand might be able to hold back a milk can as well as a cube, but not drag across the top of a milk can. Both videos were posted by the same person on 2/15/10. Maybe he was experimenting? Or maybe the man's extended hand is the answer.
https://www.youtube.com/watch?v=sRSVi5hHNzU arm slides across the top of next box
https://www.youtube.com/watch?v=vap-l8Pcyvk arm holds back next box
