The intact western "arch".
The pillars support the ends of two slabs which are embedded in the chamber
walling, these in turn, support a large lintel beam forming an arch
structure which supports the roof. The smaller SW pillar has a plethora of eke
stones above it to compensate for its low height, presumably long
thin stones were hard to find.
There would have been a second arch structure at the east but this failed when
the threshing machine brought the roof down. The arch structure
is very similar to that seen at Grain and at
other Orkney souterrains.