Firstly sorry for the bad diagram but I think it shows what I need.
In words, I have certain shapes (not those shown) that can be drag around the layout. When dropped near to another shape, the dropped one should move to, align with (i.e. rotate), and 'snap' to, the shape nearest to where it was dropped. The shapes can only fit to each other in certain way (e.g. along specific edges).
(I also need the shapes to be dragged off again (un-snapped) and to allow the connected shapes to be dragged as one, but the above is the main thing)
I'm still deciding whether to have each shape as an animation frame of the one Sprite, or to have different Sprites for each shape.
I have looked through the FAQ and forums. Some ideas come close, like magnetism effects, etc. I'm running with a couple of ideas involving lots of Pin-ing, but I'm sure there are elegant solutions that I'd not consider.