A standard channel letter is a 3 dimensional graphic sign element. Its channel is fabricated from sheet metal, most often aluminum since it will not rust. A flat sheet of aluminum is typically cut on a table by a computer-controlled router. This creates the back of the channel and is the basis for the letter shape. The sides of the channel letter, called the returns, are then formed by bending a 3 to 6-inch-wide (150 mm)strip of aluminum sheet around the aluminum back. This return can be welded at the seam or flanged and riveted to the back to create a solid can in the shape of the letter. The letter can is painted and fitted with any lighting components necessary such as neon gas tubes or light-emitting diode (LED) modules. A translucent plastic face usually of 3/16″ thick sheet acrylic fiber or polycarbonate is cut to fit the open face of the letter can. A trim cap border is applied to its edges which gives the letter face a finished appearance and creates a fastening surface to attach it to the letter can. When illuminated at night, channel letters draw the eye of passers-by.
These resemble standard letters, but the neon is covered with a clear acrylic face to keep birds from making a nest in a channel letter.
In this letter type, the face of the letter is constructed from aluminum and the lighting is directed to the back. This light floods the wall that the letter is mounted to and creates a negative space at night. Letters in this style are also called halo letters. It is usually the most expensive form to manufacture.