@EclecticHuman Never seen one of those before. It instantly brought to mind an egg insulator, used widely in communications and electricity support structures. I wonder if the recesses were for rope to lie within?

@JanPV Yes, some theories suggest the channels between the knobs could have allowed carved stone balls to be enclosed in twine or leather thongs to allow for their use as weapons (bolas, maces, slingshots) or weights.
Other theories suggest the balls might have been used in ritual or storytelling or that they served as markers of status, or even as testaments to a stone worker's skills.

@EclecticHuman @JanPV having once held a 3-D print of one of the Aberdeenshire stones in my hand my personal theory is they are calculators.
We have no doubt that people 5000 years ago were making complex calculations about celestial movements but nobody has suggested how they might have made them.

@peterbrown @JanPV That's an intriguing theory. I'd rather like it to be true!

@EclecticHuman @JanPV the difficulty is that many of these stones are slightly different. The number of lumps on each stone can vary considerably, so unless each user was using a different base for the calculations that puts the theory immediately in doubt.