A derail or derailer is a device used to prevent fouling of a rail track by unauthorized movements of trains or unattended rolling stock. The device works by derailing the equipment as it rolls over or through it.
A derailed train car at a closed siding
A derail device installed on a siding at Glen Haven, Wisconsin, oriented to protect track located off the bottom of the picture
Derail on Nemuro Main Line, JR Hokkaido. It is set so that a train proceeding away from the camera will remain on the track.
A buffer stop, bumper, bumping post, bumper block or stopblock (US), is a device to prevent railway vehicles from going past the end of a physical section of track.
Two views of a Hayes-built bumper at the Linden Railroad Museum, Linden, Indiana. This design accommodates the AAR coupler.
Energy-absorbing buffer stop in France
A buffer stop or sand drag on the Montreal Metro Honoré-Beaugrand station