# Extrude Along Alignment
A bridge model is typically built to follow an alignment. It is convenient therefore to be able to generate a model by specifying an extrusion along an alignment.
# Definition
Alignment and Chainage
Choose the alignment along which to extrude a model and the start and end chainages for the extrusion. This defines the basic geometry of the model.
Target Element and Section
The extrusion places a set of elements along the alignment. This controls both the element size and the section to apply to the bridge deck.