 Sometimes piers have vertical shafts attached to them, and may also have horizontal mouldings at the level of the base.Although basically rectangular, piers can often be of highly complex form, with half-segments of large hollow-core columns on the inner surface supporting the arch, or a clustered group of smaller shafts leading into the mouldings of the arch.Piers that occur at the intersection of two large arches, such as those under the crossing of the nave and transept, are commonly cruciform in shape, each arch having its own supporting rectangular pier at right angles to the other.