This can be done with the free Revit MEP Fabrication extension. Use the rotate command to rotate the element vertically. Placing channel cable trays upside down is also desirable, I have seen some constructions using this positioning, mainly for small size ones. 07-20-2016 09-10-2016. However, Cable Trays do have certain limitations in that the channel shape can only be set to a horizontal aspect where the bottom edge runs parallel to its supports.