An advertisement for a doujin circle, usually consisting of an empty white box with a black border in the upper left corner of a picture.
The box is there for information about the doujin circle, such as when they will be attending a convention and where their stand will be. The box is also used by event goers as a checkbox, often with a highlighter.
The circle name may be displayed prominently beside the cut, as well as textual information about what the circle intends to offer. They are usually in some standardized size, as specified by the event. They're usually monochrome for the printed event catalog, and in color for web catalogs.
Some circle cuts don't conform to this visual template exactly, but still act as advertisement for the doujin circle. They might vary in appearance from just a character's portrait and the circle name, up to entire small scenes or comics whose purpose is to announce the booth number.
Pixiv
Twitter
Bluesky
Weibo
Lofter
Tumblr
