Ladder

A ladder is any stackable structures that feature ladder on its side, allows an engineer to climb vertically.

It may refer to: (sorted in image from left to right)
 * Conveyor Pole Stackable
 * Pipeline Pole Stackable
 * Hyper Tube Support Stackable
 * Storage Container
 * Industrial Storage Container
 * Fluid Buffer
 * Industrial Fluid Buffer

Buildings that are non-stackable, but feature long ladder:
 * Lookout Tower
 * Radar Tower