What is outline or single built-up letter?

An outline or single built-up letter refers to a type of signage where the letter is constructed from a three-dimensional shape, often made of materials like metal or acrylic, but only the outer edge or outline of the letter is illuminated or colored. This design creates a striking visual effect, highlighting the letter’s shape while maintaining a sleek appearance. Commonly used in signage for businesses, these letters can be backlit for added visibility at night.