These angles are designed for mounting garage door openers, building frames, table, work benches, equipment stands, etc. and for many repair and construction projects. They are slotted for easy attachment. This product has a 90 deg. angle and slots that allows product to meet a variety of applications. Fasteners can be applied through slots to affix product to a surface. High corrosion-resistant galvanized finish. Made of steel. 1-1/4" thickness. National catalog model No. 4021BC.