Vent covers allow the vent to be open during inclement weather keeping moisture from entering your rig. Pretty easy to install without removing vent itself as they mount to the side of the vent flange. One of my favorite mods, sure wish they would come from the factory per-installed as they are relatively inexpensive. Various reasons for bringing an extra ladder include using to mount roof, especially if ladder attached to the rig is suspect, accessing the top half of the RV for checking awnings, lights, seams, vents, satellites, antennas, we use it most often for cleaning bunk windows we have just inches below the roof line.