- I need the rods + add-a-rod for sliding glass doors measuring 72" in length. I want to hang sheers behind light-blocking panels. How can I get the add-a-rod (for the sheers) to extend the length of the doors so it lines up with the regular rod (for the panels)? I will likely have the regular rod extend about 76"-80". Is it possible to combine 2 add-a-rods? Is there a way to support the center so it doesn't droop?