Guy Litespeed

Many thanks both. The gaps in the walls don't have doors, so I think the second theory is most likely to be correct i.e. they're for slate in or out. My best guess is they were for waste slate, out?

In the process of building my first ever railway. Making mistakes everywhere, but learning heaps! Does anyone happen to know what the ‘Low walled vents’ were for on the Bachmann 009 slate processing building? See attached pic. Thank you!