Channel letters are the type of signs you often see above large franchises. Letters and graphics formed from aluminum and illuminated with LED's. There are three main styles, face-lit, halo-lit, and non-illuminated. These are further explained below.
A raceway is an aluminum channel that runs behind the entire set of channel letters. It houses the wiring and the power supply. This method requires that only one wire be fed to the sign through the wall of the building. It also makes it easier to relocate the sign to a new location. More than one raceway may be required depending on the overall shape of the sign.
Flush mounting involves mounting each individual letter and component flush to the wall. A wire has to be fed through the wall behind every letter to a power supply located behind the wall. The benefit of this method is no raceway is visible and the power supply will generally last longer because it is not exposed to the elements. The drawback is that many holes need to be drilled into the wall to accommodate this type of sign.