Berkshire History for Kids: Abbey Building 05

What's Building No.5 used for?

This building is medium sized.
It is built over the river.
It has two storeys.
The lower storey is not a room, but has the river flowing through it.
The upper storey has small windows.
Inside, there is a long wooden bench along one wall. There are large holes in it. Each hole is open down to the river below.
It is near the building with the beds (No.4).