They are commonly used on docks and on playground equipment or in cases where it may be difficult to reach the bolt head with a tool.
5 & ASTM A307A Due to that reason, they are often used when a more aesthetic look is desired.Size: 5/16 inch-18 X 3 inchFeatures a smooth rounded head as opposed to a standard hex headSquare shoulder allows for nut to be tightened or loosened Often used in cases where a protruding bolt head could cause injuryNuts and washers not included, ensure washers and nuts are same diameterThread Type: Coarse, Thread Class: UNC-2A, Point Style: BluntSpecification(s) Met: ASME B18. The square shoulder on carriage bolts help to hold it in place while the nut is fastened..