here's a pic of my trailer, sporting these covers whilst parked in the PO's back yard. I was under the impression that they had these made up from an old awning...perhaps they were store-bought? same vinyl material that was used on the original rear-window awning, which is still in use. (not visible in the pic, though).
3 snaps attached to the skin, just above the wheel wells.
I haven't been using them.
probably should be, although, I will say that I am parked in the shade most of the time. But I just "re-tired" (doh!) the PO's tires...9 years old, according to the DOT tag, and they looked brand-spankin' new. hated to do it, but the "replace by age, not wear" advice seems fairly universal.
Anyway, perhaps the regular use of these covers explains why they looked so new, and lasted so long.