Rats and mice can still get up into their entrance hole by crawling up the tires or any other object that hangs to the ground.
My trailer sits in the trailer shed out by the barn so mice/field rats are around 352 days a year.
I use hardware cloth over all holes and louvers and lots of spray foam closing any cracks that insects and rodents can use to get into the trailer.
I use Tomcat baits in the barn and trailer shed. The bait forces them to seek water. With no water they leave the barns and later die.
I keep a mouse trap/peanut butter just inside the trailers door and check it maybe once a week. Its rare one is in the trap but if I trap one I set out 2-3 more till the family is all trapped out. Then I look for and seal the entrance hole.