Double-struck is also called "blackboard bold" because the look originates from mathematicians using the edge of a piece of chalk when writing, to create bold-looking letters on a chalkboard. Over time, the letter-style became distinct from bold and moved from the blackboard to typed and digital forms. Mathematicians use this style to represent sets and other types of variables. On social media, text with an outline-looking font is often used to create visual impact and draw attention. It provides contrast against backgrounds and looks very unique. Additionally, outlined fonts like double-struck can add a decorative flair.