The squeegee is the most important tool in the professional window cleaner’s arsenal, so much so, that you wouldn’t find a window cleaner who doesn’t own one. They’re brilliantly designed to feature a rubber-edged blade set on a handle and they scrape away the dirty water, leaving the windows sparkly clean with no drip marks whatsoever. They work so close to the surface that no water is left behind.
You generally apply the squeegee to the surface after you’ve washed them with window cleaning liquid and water. Then after the using the squeegee it’s usually a case of wiping down any dirt marks on the seals or the frames surrounding the window. Nowadays they have extendable squeegees to reach from a distance, and some window cleaners don’t even need ladders because their tools are all extendable and the squeegee completes the job, never leading any watermarks at all.