Curtain Slider

Curtain Side Trailer
A curtain side trailer is a specialised semi-trailer that has a rigid framework mounted onto a flatbed or flat-deck trailer.
Curtain side trailers are comprised of a firmly bolstered front, which features an entry door, horizontal roof supports running the trailer’s length, a metal constructed roof (similar to a dry van’s), two swing-open rear doors and a sliding tarp system — typically made from an 18-ounce (or similar) material.
The tarps on either side of the curtain side trailer can be retracted for loading, sliding in a similar fashion as the tarps on a Conestoga trailer.

Confused with a Conesoga
Not to be confused with a Conesoga (though they commonly are), curtain side trailers are different in a number of ways. Most notably, curtain sides only feature tarps on two sides (the left and right). Conestogas have a larger curtain system which creates its roof and rear as well.
Additionally, curtain side trailers feature a far more rigid framework than Conestogas do. The roof of a curtain side trailer is immobile and not retractable — the same cannot be said of Conestogas.
Curtain side trailers come in both 48 and 53-foot variations. Here is a list of the maximum cargo dimensions for this trailer type.