I was wondering if anyone could help me design an aid for my pet rat that has hind leg degeneration. I have a long slope where i can train him to climb on some kind of trolley and was thinking his weight would release a brake and a weight would pull it up the slope. the tricky part (for me anyway) is getting the trolley back to its original position at the bottom of the ramp. The rat can climb down with out any aid on its own. Obviously, both up and down need to move fairly slowly.