A vertical barrier, consisting of toprails, midrails, and posts, erected to prevent employees from falling off of a scaffold platform or walkway to lower levels.

Barriers along the edge of the roadway to protect something from the impact of an errant vehicle. DOT now prefers to use the word guide rail, because they are now designed to deflect as well as absorb the impact from a collision. While the most common rail on the Henry Hudson Parkway is now galvanized steel W beams, it also preserves original ornamental green steel fencing in Manhattan and rustic wooden rails in the Bronx.

The thing that separates the men from the boys according to Signal Auto's Fumiaki Komatsu. Hawaii Motorsports Center's got lots of them.