This stone is situated by itself on the North side of Knockhill Farm, just to the East of the modern stone circle, and South-East of Cairnpapple Hill. Click here for a location map provided by StreetMap.
The Knockhill Stone, Looking East
While this stone appears to be a genuine standing stone, its current position is not original, being placed on top of an early modern slag-heap from the Hilderston Mines. Indeed, the Ordnance Survey map for 1856 gives its location on the North side of the mines, on the other side of the glen. On this map, the current location is more-or-less where an old kiln is marked at "The Knock" farm:
Knockhill Stone, OS Map, 1856
Presumably, the Victorian farmer at Knockhill had the stone moved at some point after 1856, rather than have it destroyed by the mine workings, and so its modern use has probably been as a cattle rubbing-stone. Certainly, the smoothed indents along its sides suggest such just a use.
The Knockhill Stone, Looking West and East, Respectively
Nonetheless, the stone appears to be genuine, and is definitely old, presumably bearing some relation to the nearby henge and circle at Cairnpapple. Indeed, it may once even have functioned as an outlier to the circle at the larger site.
The Knockhill Stone, Looking South and North, Respectively
Today, though, its position is fortuitously as an outlier to the new stone circle erected by the modern Knockhill farmer as a birthday present to his son in the 1990s:
The Knockhill Stone Circle, Looking South-West Towards the Knock
The Knockhill Stone in the Distance, Looking North-East from the Modern Circle
Knockhill Farm seems to have become rather affected by its proximity to Cairnpapple, because not only do we have a modern stone circle there, but at the farm entrance, a modern carved boulder complete with "Pictish" boars!
Modern "Pictish" Stone, Knockhill Farm
Overall, it seems that the tradition of farming at Knockhill is one which has respected the local ancient remains to a commendable degree - unlike certain other modern farms in the area which have actively destroyed ancient stones, Knockhill has, in times past preserved one, and today, deliberately attempts to emulate their style.