Tall Rail Post

Tall Rail Posts are a railway item in Astroneer. They allow for the creation of rail lines, and can be used to recall Rail Engines to it. They are a tall version of Rail Posts, allowing for taller sections of rails.

Source
Tall Rail Posts are placed from a.

Uses
Placing a Tall Rail Post within range of another will connect a rail line between them, deforming any terrain that might be in the way.

Tall Rail Posts may be placed on any terrain, allowing for placement on walls and ceilings of caves.