Somewhere I have a pic of a German army farrier back between the world wars, with a big old artillery horse with his foot perched up on one of those. Beats holding it!
I imagine you’d REALLY have to have one while working on draft horses. I mean, dang, their feet are as big as my head. Some people will only shoe big horses like that or problem horses in a “Shoeing Stock”. It’s like the stocks they have at the vets office, but it has places where you can tie each foot to a support as you’re working on it so they can’t take it away from you and the stocks keep them from getting away. I’ve never seen one used though. I’ve just heard about them from an old guy around here who likes to mess with Belgians. I think he built one.