Trailer Vents

[Dale99]

So I bought an enclosed trailer to haul my toys in. Got a hold of an AC unit for cheap price and put that on it for when I spend the weekend out at the atv parks. But now I realized I have no venting for when its not in use, or even traveling down the road.

Ive found the "salem" vents, or also known as 2 way vents. So questions on these. Do they just screw or pop rivet in the outside, and then the inner normal plastic part just also screw to the inside? Do I need one side of these to screw into an upright rib?

Next, I normally have noticed the front vent is up high, and rear vent down low? This seems kinda backwards to me being I live in a normally hot climate. I would want cold(low) air coming in up front, and my hot air coming out the rear (high). Can anyone explain why they are the way they normally are?