SQUARE HOLDING DOWN BOLTS
This type Square Holding Down Bolt have a square shaped external wrenching head and are usually used with a square nut. They are used in all types of industrial, agricultural, and construction applications. Their square shape makes them well suited for use in tight areas where the bolt is tightened blind.
The same applies to hexagon bolts, they’re easy to tighten and loosen because of their shape. The reason they’re hexagon nuts and hexagon bolts and not pentagon or octagon is because the side 6 of a hexagon give enough faces for a tool to grip, but not so many that it’s easily rounded off through use over time.