text-combine-upright CSS property sets the combination of characters into the space of a single character. If the combined text is wider than 1em, the user agent must fit the contents within 1em. The resulting composition is treated as a single upright glyph for layout and decoration. This property only has an effect in vertical writing modes.
This is used to produce an effect that is known as tate-chū-yoko (縦中横) in Japanese, or as 直書橫向 in Chinese.