This option is for changing the width of a road or footpath along its length. This is done by editing the items that define the channel or back-of-footway (i.e. the parallel, widening, and mitre items that define the designline).
If you have not yet added any channel items for the selected channel or back-of-footway, the design line will be composed of a single parallel item with an offset matching the value entered in the Channels/Kerbs/Footways window.
To access the tools for modifying channels and footways click the button and select the Channel or Footway you want to modify. Select the Edit Channel/Footway button.
You can now use the mouse to select a channel/footway item.
As you move the mouse over other items you may notice the items drawing in different colours. Green items are Parallels, blue items are Widenings/Narrowings, and yellow items are Mitre Corners. The item which is the mouse is currently over is indicated with a red/orange highlight.
After clicking on an item a window will pop up allowing you to change the properties of the selected item. This will depend on which item was clicked, see the following help pages for more information:
Note: This tool does not select amorphous items. Click the Amorphous Channel button to edit an amorphous item.