Use the z-mod vertices tool

Steps

1. Ensure the z-mod area (polygon, line or point shapefile) is selected within the Layers panel. On the 2D Build tab, within the Z mod section, click Z mod vertices to open the tool in a new window.

2. Your selected shapefile is provided in the Input Shapefile field. If required, use the drop-down to browse to other shapefiles loaded in the Layers panel, or the button on the right to browse to other (unloaded) shapefiles.

3. Drag the DTM (or other grid containing your elevation data) into the field provided. This data will fill the vertices of your shapefile area. You can add multiple files here if required; values from lower layers in the list will take precedence.

   Tip:

   Uncheck the box Update heights from DEMs to not select any files. In this case, the vertices will filled with -9999 data (to be edited manually).

4. Click Process and text to the left of this button will appear to confirm when the process is complete. Close the tool and a new shapefile will now be added in the Layers panel. Contained in this shapefile are the vertices of your initial shapefile, filled with the data from the grid, 

   Note:

   By default, the new shapefile has the name of the initial shapefile, proceeded by -zpoints, e.g. MyInitialShapefile-zpoints.