When we visit a monastery it is easy to imagine that it was just a large church, but it was far from that. For one thing the nave was split into two separate places of worship. The eastern end would be for the monks themselves and would have had two chapels each side of the main altar. The monks would have sat in choir stalls facing inwards.
It was in the western end that the lay brethren worshipped. Even monks had to eat so the lay brethren were responsible for tending the fields and the animals, the cooking, laundry and even cleaning the toilets.
The two sides of the nave would also have been separate.