This is an Austram Product no longer available and a wonderful design.  It can be used to wall mount a trough style planter or would support a shelf in the garden room or above the planting bench.  The second photo, below, shows it in use at my shop supporting a display of deck planters.

Each bracket measures 12.75" tall and 8.75" deep - mounting screws and jackets are provided.  The bracket will hold a planter or shelf up to 7.5" deep.  It is made of steel, zinc coated and completed with a powder coated finish in distressed verdigris.