In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

The top is held in place with?, Context: Inner and outer vestibules lead to the octagonal chapter house, which is of exceptional architectural purity. It is built in a Geometrical Gothic style with an octagonal crypt below. A pier of eight shafts carries the vaulted ceiling. To the sides are blind arcading, remains of 14th-century paintings and numerous stone benches above which are innovatory large 4-light quatre-foiled windows. These are virtually contemporary with the Sainte-Chapelle, Paris.
eight shafts