We purchased two portable air conditioners for our bedrooms. It include a plastic window kit that can be fitted for the window. I.e., this:
I need to trim off about 6 inches, which requires a simple straight cut. Doing it by hand is challenging -- both physically and to get it straight. (I took that approach years ago, with a different unit, in my apartment.)
This time I have a circular saw and realized that would be a lot better and cleaner. However, I'm not sure if I need a special blade? Currently I have 18- and 24-Tooth Saw Blades.