err how big are the ponies?
ummm quite difficult I guess unless you just split it down the middle??...not quite sure how it would work though and for door entrance?
There's a Section A and a microscopic Shettie at our yard and they happily share a 12 x 12 stable with no partitioning. 2 haynets are hung at opposite corners of the stable and they are fed separately. Mind you, they were friends before this arrangement and were watched like hawks for the first few hours. Happy as pigs in clover now.
We've dont this with one of our stables for my shettie and exmoor. We got 2 sheets of thick 8'x4' ply, a load of 3"x2" batoning, 2 hinges and a stable door bolt. We made a frame to attach to one wall of the stable and up to the rafter in the roof. We then screwed it to the wall, floor and rafter then screwed the one piece of ply on one side. Out of the other piece of ply we cut a 4'x3' high door attached with the 2 hinges drilled a hole in the wall so that when you put the door bolt on it pushes into the wall. Hey presto 2 stables in 1 with a door.
I had to do this the other month as a pony had cut itself at another yard so was brought over to my place. I went to the nearest diy place and got some pallets from them for free checked for nail then screwed them together and then to the wall in the middle. I then put two hinges and a lock bolt on one pallet to act as a door and put one brace from floor to roof and the partition is as strong as an ox. It was a cheap fix in an emergency but 3 months later its still as strong and as the pony has stayed with us the partition is staying as well.