screentones by themselves are basically patterns made using dots. In the old sense anyway. When it comes to comics and manga, they can be anything from backgrounds to small dots close together to big dots far apart. In manga or comics, they can be applied digitally (the more common method now), or they can be applied traditionally. In manga they are transparent sheets of "sticker" paper for a lack of a better term. You lay the paper over the comic and use a blade to cut out (via tracing) and then once finished, place the tone on top of the comic to give it tone! I can't afford to buy any at the present, so I bought transparent sticker paper that you can print on and I'm making my own.

When it comes to finding patterns to use, you can either scan in tones to use digitally or find stock that you are legally allowed to use and use it. That's what I've been doing. XD Or if you have even basic art software and have patience, you can make your own tones from scratch. ouo Below are examples of hand made ones (left) and a professional one scanned in. (right)