Our basic stall latch works perfectly for our Arabian gelding. Arabians are often compared to Border Collies when it comes to intelligence. In my experience they do tend to be clever equines. When it comes to stall latch opening, our particular Arab is no Einstein however.
My Appaloosa mare quickly learned to simply lift the latch up with her lips and then slide it sideways with her teeth. The Quarter Horse caught on fairly quickly too. Both mares will do this without a second thought in front of us.
So, to keep the mares in their stalls, we added the large snap. This blocks the horses from flipping the latch up. Effectively, we figured they were confined. This method does work for the Quarter Horse mare. Not however, for my clever Appaloosa!
But the Appaloosa mare, Cinnamon, would carefully turn the large snap sideways, so she could then lift the latch over it. The addition of the smaller snap has prevented her from turning the large snap – at least so far! With the double snaps she is confined for now.
Now, if we look at this situation as a test of intelligence, clearly Cinnamon is the Einstein of the barn. On the other hand, perhaps she just has more facile lips. Or she simply likes to tinker with things. Maybe she is the fastest eater and so has more time to fool around with things. I, of course, feel she is simply brilliant. What this example does show is that intelligence in the horse is not as easy to figure out as we might think.