I was trying to lock a gate on a sim's property so the horses can't get in to eat the garden plants. When I clicked the gate it give the option of "pets". I assumed this meant pets would be locked out. But I got curious and clicked lock again, but this time used the "specify sims who can/can't use this door" What I saw was two huge lists and every cat or dog in town listed as someone who can use the door and on the other side, all the sims in town under cannot use door (aka gate) This was weird and I'm not sure what I did there. But also, what's up with that I didn't see ANY horses listed on either list?? Do the horses get locked out too and this is just a strange glitch? Or will horses still be able to get into the fenced in garden?

The best way to specify who can and can't open a door/gate is to first have your sim selected, then click on the specify sims option and choose allow me only... (or something to that effect). Then click on specify sims option again and the only one on the right who CAN open the door/gate will be your sim. Then you can look down the left side list and choose who else can be put on the right side or remove the sim from the right so nobody is listed. I often do this with doors to the kitchen in open diners. Then I can remove my sim from the right side and add only the waitresses and cook to the right sided. This way it stops every sim in the neighbourhood from being on the CAN side.
The lock for pets should keep all pets out instead of specifying your pets, unless you want the horse out and the cat in