These are the passages on Poku Saeruo Degonjo vessels for moving from one deck to another.
Vertical transfers are either staircases or ramps. Normally smaller vessels tend to use stairs, while larger ships will be fitted with ramps. Regardless of the format both have isolation panels that in the event of decompression seal the transfer off between decks.
Climb shafts are sealed during normal ship operations. During alerts the are unsealed but left closed. These are typically placed to facilitate crew members getting to vital stations When a crew member pulls open a door there is a narrow shaft going up and down that is fitted with a rung ladder built into the back wall. They are opened by pulling on the railing that is attached.