Gridirons would be able to be built under any gate and what it does is prevent animals which are unleashed to walk through the gate.
You could still go through them on horses once you've mounted them, but this would imrpove quality of life for big animal pens where everytime you open it 5 sheep escape.
Of course with changing setups you can easily work around this, however I find that if you make it a fair cost this advantage may be granted.

This is what it looks like in real life.
I know that if an animal has a rope on their neck or you're on top of them it does not help them get over it. But it's a game

Thoughts?