Trailer In A Bag What Decides Who Goes In When While Using A 3 Horse Slant Load Horse Trailer ?

What decides who goes in when while using a 3 horse slant load horse trailer ? - trailer in a bag

I would buy for my three horses, which are all different sizes and chargers to carry. A horse is high h) (16, one is small (POA - 13 clock) have not much experience with the cargo, maintenance costs, but many supporters. Since no investor ensure that these trailers with bags of food or not. Thank you, Northern California.