what does it mean to jackknife a trailer
Jackknifing Jackknifing refers to the folding of an articulated vehicle i.e. one towing a trailer, such that it resembles the acute angle of a folding pocket knife. If a vehicle towing a trailer skids, the trailer can push the towing vehicle from behind until it spins the vehicle around and faces backwards. This may be caused by equipment failure, improper braking, or adverse road conditions such as an icy road surface. In extreme circumstances, a driver may attempt to jackknife the vehicle deliberately in order to halt it following brake failure. A jackknife event of a heavy vehicle can be fatal to the driver as the top of the cab can be crushed or sliced off as it swings round violently and tries to fold under the trailer.[citation needed]
Trailer (promotion) A trailer (also known as a preview or coming attraction) is a commercial advertisement for a feature film that will be exhibited in the future at a cinema, the result of creative and technical work. The term "trailer" comes from their having originally been shown at the end of a feature film screening.[1] That practice did not last long, because patrons tended to leave the theater after the films ended, but the name has stuck. Trailers are now shown before the film begins.