Reverse channel letters are often called halo-lit signs and are built the opposite of standard channel letters.
They are manufactured of aluminum, welding faces with returns and illuminated individually by neon tubing placed behind the letters. These metal letters are then separated a couple of inches from the wall which creates a halo effect around each letter.
During daylight hours, reverse channel letters look much the same as standard channel letters. However, at night they take on a very unique "halo" appearance providing a distinctive look that is softer and more elegant than that of its standard channel letters counterpart.