The Glider was designed to spread cleaning solution across from your area of access to the other side. That means you get your window cleaned evenly. And while it's cleaning the outside, it will also clean the inside.
Getting your windows professionally cleaned a few times a year can add up. Using this gadget allows you to clean your windows more frequently.
You won't be able to wash the outside of windows that don't open since you won't be able to place the gadget. However, if you can access the window, you can easily wash the inside and the outside. I love getting twice the results for half the work. You also need to be aware of the thickness of your window. There's different models for each so that the magnets hold properly. It gets most of the dirt and yuck off without leaving streaks, so it's worth looking into.