Shackles are sized according to the diameter of the bow section rather than the pin size. Never use a shackle if the distance between the eyes is greater than listed in the manufacturer's tables.
Consult with the manufacturer if using shackles in extreme conditions (e.g., temperature higher than 204°C or lower than -40°C, or exposure to corrosive fumes).
Use a shackle when 2 or more ropes must be placed on a hook.
Do not replace the shackle pin with a bolt or unidentified pins. A load will bend the bolt.
Do not allow a shackle to be pulled at an angle. The legs will open. Pack the pin with washers to center the shackle.
Do not use screw pin shackles or fit pins in contact with moving parts if the pin can roll and unscrew. If the load shifts, the sling will unscrew the shackle pin.
Do not use round pin shackles restrained only by a cotter pin for overhead lifting.
Do not use shackles with bent pins or deformed bodies.
Do not force, hammer or wedge shackles into position.
Do not exceed 120 degrees for the angle when using multiple leg slings.