Standard Letters/ Logos:
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 4- to 6-inch-widestrip 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 light-emitting diode (LED) modules. A translucent plastic face usually of 3/16" thick sheet acrylic 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.
Front/ Reverse Illuminated Letters:
These letters have the biggest impact. The face of the letters are illuminated and the back of the letter. Standard LED color is white, however, there are other color possiblities. The back of the letter has a clear or white polycarbonate or acrylic face instead of aluminum. The below photos of Platypus have a day-night vinyl face. During the day the letter looks black.