According to the direction of the strap, the elongated section of plastic should face the front.
But… it looks really weird.
Is that correct?
The boot on the top in the picture goes on the left hind. Sometimes there is a double layer of Velcro so the actual strap ends faces back, but the top extra Velcro hold faces forward
That’s what I figured… to wrap “tendons in” with the tension.
It’s just that off-shaped piece of plastic that doesn’t make sense. Ah well, knew there must have been a reason they were on sale! 
The rounded plastic piece sits on the inside of the fetlock joint. The velcro faces out on the outside of the fetlock joint. There should be very little “tension” (think “snug”). Gravity basically keeps them in place, along with the contour of the fetlock “cup”
If you search for “hind fetlock boots” you will find ads with photos.
lol, that part I get.
These particular boots have an elongated side to the plastic. They aren’t an even “gourd shape”. The straps indicated that the elongated portion should go towards the front of the horse, but it looks funny to me. Alas, I think that’s the way they go.
