The following comes from "The Owner Groom", by T. Howe, (Country Life, London, 1938). "The turned down ends on horses shoes. Shoes with calkins give a surer foothold than a plain shoe, but have the disadvantage of keeping the frog" [the sensitive centre part of the sole of a horse's hoof] "from entire contact with the ground".

The following comes from "Horses and Stables", by Lieutenant General Sir F. Fitzwygram, Bart., (Longman Green, London, 1903). "Calkins are used generally as a stay to the foot, which may be needed in heavy draught work or on slippery ground ..." The gallant Lieutenant-General goes on some more, and concludes "Calkins are utterly inadmissible on the fore-feet".

In this book, there is also an illustration of a shoe with calkins. The best way to describe them is to say that they are like giving a horse low high heels.

So Mike Jefferson, in his original enquiry, has correctly described what calkins are. It must be said that, in farriery terms, it would seem that Kipling didn't really know his rasp from his Charlier!

I think that Kipling, as I think we will all agree, liked to show how clever he was by the use of all sorts of technical terms. It is more than possible that, being in mountainous country, the 'colonel's mare' might well have been shod with calkins on her shoes, but the point is that the two books I've quoted show that the calkins were an integral part of the shoe, not a 'bolt-on'. And there is no way you can reverse a horse-shoe on a horse's foot - or not so that you can ride the animal safely, nor in the ventre-a-terre manner described in the poem.