I made these Steps out of a 3mm x 3mm Manzonia wood. I had to cut it into a triangular and then hollow it out with my Dremel and a cylindrical bit.
The Steps are 11mm long with 11 per side.
As usual, I used Contact Cement and CA Glue.
Also, chopping the wood, I used my Xacto and pressed it down really hard.
I’m not too worried about the Ladders being exact. I’m sure in a working ship, those Ladders were constantly being battered and always had to be maintained and replaced.