Dutch to English Tech/Engineering Ships, Sailing, Maritime Instructions for working at heights

I am translating a document containing instructions for employees that work at heights onboard ships. I've been translating (Vaste) Stellingen as scaffolding, but now I came across a list of items containing Vaste Stellingen and bouwsteigers as two separate items. As far as I can tell Bouwsteiger is nothing more than scaffolding, but I obviously I cannot list scaffolding twice.

I would greatly appreciate it if someone can explain the difference between the two for me.

TIA