The previous owners of the house left a six foot long bamboo pole in the garage. I attached the bent corner bracket to the bamboo with screws. Bamboo cracks and splits very easily. To keep the bamboo intact, I wrapped it and the corner bracket tightly with two layers of plastic electrical tape. This photo also shows the proper "U" bend in the corner bracket.
A piece of pine 3/4 x 3/4 inch would have worked, too. I just happened to have this piece of bamboo for which I had not other use. Some pine could have been sliced off of the edge of a board.