The jack has 4 wheels so as you are jacking up it slides underneath the mower.
The MoJack only has 2 wheels and they are only for moving it into position, so it won't move as you raise the mower. And since I've only used mine in the grass in the yard instead of on a hard surface, it wouldn't move anyway. And my Toro has an unusual (to me at least) feature that I'm not sure I like. The MoJack manual says the mower has to be in "neutral" as you raise it. Well, the Toro has an electric brake; no problem I reckon, as long as you know about it. I not only pull both handles in, but I also have to turn the key on to release the electric brake.