To properly dimension a cable tray/duct/pipe covered by a rise/drop symbol follow these steps: Turn off the rise/drop display components of the ducts in visibility/graphics from the respective model categories. Dimension from the edge of the cable tray/duct. Dimension Rule Horizontal dimensions are placed on vertical. Download our AutoCAD drawing featuring plan and elevation views of a cable supports tray, also known as cable trays or wireways. Was this information helpful? Need help? Ask the Autodesk Assistant! How to create a.