DO NOT HUMP

In railroad terms, "humping" refers to the use of a track laid over a hill or "hump" in classification yards. Train cars are decoupled on top of the hump where gravity then separates them and imparts the speed necessary to carry the cars to their respective destinations. Even though their speed is regulated, cars are often shunted to one another with some residual momentum (they can bang together pretty hard). Pictured here is a train car that ferries fully-fueled sections of the Space Shuttle's Solid Rocket Boosters. The last thing you want to do is subject several hundred tons of rocket fuel to an impact. Hence the large signs reading "DO NOT HUMP." And you thought it was about frotteurism on Wednesdays.