Polylines can be automatically chained together by computing new segments between unconnected points.
Open the file SectionsBuildingPlan.3dr (download).
You can chain the polylines of the group Lines to chain. Select the polylines and go to Chain Polylines. Uncheck all the options.
Polylines to chain
Automatic chaining of polylines
Note
Polylines can also be grouped in a set of polylines. After creating the planar sections on this file (Exercise: Create planar sections on a mesh (extract contour lines)), we could group the polylines and create one set of polylines per elevation.
A set of polylines can always be exploded into individual polylines by using Ungroup Polylines.