--- title: "Z-Lines | Technical Reference" slug: "z-lines" description: "Learn how Z lines allow users to define the elevation along a polyline based on the elevation at two or more points snapped to the polyline. " tags: ["2D modelling"] updated: 2022-07-29T11:19:23Z published: 2022-07-29T11:19:23Z canonical: "help.floodmodeller.com/z-lines" stale: true --- > ## Documentation Index > Fetch the complete documentation index at: https://help.floodmodeller.com/llms.txt > Use this file to discover all available pages before exploring further. # Z-Lines 2D solver supports Z-Lines which allow users to define the elevation along a polyline based on the elevations at two or more points snapped to the polyline. In the simplest case, a Z-Line consists of a polyline with two or more vertices with a point snapped to each end. The elevation at the start and end of the line are defined in the "elevation" or "height" attributes of the points. A polyline must have a point snapped to each end and may have one or more additional points snapped to other vertices along the polyline. All points must snap to a polyline. Z-Lines can be specified in the 2D solver user interface, or directly in the XML file using a topography tag as follows: ... GIS\zLineTest_001_Line.shp|GIS\zLineTest_001_Point.shp ... The topography tag must contain the name of the shapefile containing polylines, followed by a pipe character ('|'), followed by the name of the shapefile containing points.