Most common installations are on a vertical wall, but the AB40 Horizontal Adapter Bracket can serve as a horizontal adapter for the MM340, MM540 and MM700 mounts, providing a 90-degree bridge between their wall plate and the TV mount lifting arm. This allows the wall plate to lay flat on a horizontal surface such as a large shelf or inside a recessed alcove. Another application for the AB40 Horizontal Adapter Bracket is as a pass-through support for the when mounting the MM340, MM540 and MM700 mounts to thin brick facades or simulated stone panels made from foam, neither of which are strong enough to support the weight of a MantelMount.To order an AB40 Horizontal Adapter Bracket go here.NOTE: The AB40 is not intended for use with the MM750 mount.