Hi Tobbe,
Note that after selecting an object (in Remus' case a group), you don't have to click on it with the move tool but you can click anywhere. If you create that offset to guide you, you can click on a midpoint of it, start the movement and click on the midpoint of the other, opposite line for instance. The leg will move accordingly.
Oh, by the way, hitting Ctrl+Move will make copies of your legs.