There are around 20 jostle stones in several lots with modest estimates, seemingly grey granite with a provenance to the original St Pancras station, at Wellers forthcoming 'Lady McAlpine Estate Clearance Charity Auction' at Fawley Hill on 22 May which has around 180 lots of stone, brick, and machinery.
 
Jostle stones were traditionally placed at ground level, particularly at the salient corners, of the walls of buildings to protect masonry from being scoured when the axle tree lynch pin in the iron hubs of horse-drawn carts and carriages were driven too close to the walls. A knob of stone at ground level threw the wheel away from the wall to prevent contact, and this in turn threw, or jostled, the occupants of a carriage into each other, shoulder to shoulder. They were also placed at the foot of gate piers, columns or porte cocheres.
 
Vitruvius, the Roman mechanic and builder, put it simply in 49BC:
'The roads should be encompassed at steep points, and planned so as to approach the gates, not in a straight line, but from the right to the left; for as a result of this, the right hand side of the assailants, unprotected by their shields, will be next the wall. Towns should be laid out not as an exact square nor with salient angles, but in circular form, to give a view of the enemy from many points. Defence is difficult where there are salient angles, because the angle protects the enemy rather than the inhabitants.' The need for circular protection is achieved by placing a jostle stone at a salient which makes wheels to take a more circular route around corners to protect a wall. The action when a wagon fails to observe this nicety and gets to close to the salient is a violent jostle to passengers, animals or goods.
 
The word 'jostle' - push, elbow, or bump against (someone) roughly, typically in a crowd - 'late Middle English 'justle', from 'just', an earlier form of 'joust' from 1200. The original sense was allegedly (Oxford English Dictionary) to ‘have sexual intercourse with’ and the current sense is known to date from the mid 16th century.
 
The late Sir William McAlpine who acquired the aforementioned jostle stones to be auctioned from St Pancras station knew there was a special architectural term for them - he recollected that they were glinters which, again from Middle English means to slip or slide, probably of Scandinavian or Icelandic origin - which perhaps belies his Scots ancestry although there seems no documented use of the word that we could find. Although jostle stones are a known term in England, the term seems more common in Scotland, but seems even more common in Ireland (see the example illustrated in Dublin City Council's Conservation Paving leaflet). Elsewhere the unevocative term 'wheel guard' seems to be in common use in ordinary modern architectural circles.
 
French for the jostle stone is 'chasse-roue' which translates as wheel hunter or chaser. Flickr has many here https://www.flickr.com/search/?text=chasse+roue and it would not be surprising if the French have a larger number than elsewhere because many of their rural buildings are of a softer limestone that is more easily damaged by iron cart hubs and which benefits from greater protection.