Flat Roof Corner Fittings for Canopy Frames - A1Tarps.com
Amazon.com: Extra Heavy Duty 12 Pack L Type Flat Zinc Plated Steel Corner Braces Angle Brackets 2.5" x 2.5" with 1/2" x 6 Screws : Industrial & Scientific
Everbilt 2-1/2 in. Zinc-Plated Flat Corner Brace (4-Pack) 15295 - The Home Depot