The 20cm window washer that has a sponge on one side, and a squeegee on the other. The base is connected to a 22cm pole. The pole has a grip handle with a hook for the window washer to hang on a wall.
This allows one side to be used to wash, and the other side to remove the water / soap from the surface being washed.
This could be used for windows but also for applications such as washing vehicle windscreens.