Trim caps give the lettering of a channel letter sign a finished appearance. They create a fastening surface that attaches to the return of the lettering. They can be required if using traditional fabrication methods. Despite their ability to create a finished appearance, there can be some downsides to having a trim cap. Trim caps are prone to gaping between the return and the face and having a wavy border. Additionally, they may stand out more than is desired since the trim cap’s color may not match the face of the lettering, and it can be hard to paint. Over time, the cap may direct water to drain inside of the lettering, resulting in a dirty face and mold growth within the sign.