Regardless of shackle body type, the load pin or bolt on a lifting shackle is fastened through the shackle body in one of various different ways.
One of the most common configurations is the threaded bolt or screw pin type - the threading on these pins may be complete on occasion, but more often it will only be partially threaded, to allow for a secure connection with the shackle body but without adding friction to the payload attachment elsewhere along the length of the pin.
Screw pin shackles are generally well suited to most temporary applications, provided there is no risk of the load moving significantly while supported. In some situations, this can potentially rotate the pin and gradually back it out of its threading. If a screw-type pin is deemed suitable for a particular task, one of its key advantages is that the entire shackle setup will consist of only two parts, and be notably quicker and easier to assemble/disassemble.
The other common type of shackle pin is the safety bolt version, in which a split pin holds a nut and bolt in place, acting as a clevis. The shackle then becomes effectively a three, four or even five-part component, which will be inherently less easy to set up and work with than a two-part screw pin shackle.
However, a safety bolt pin is far better suited to use in permanent connections, or in scenarios where there is liable to be some movement of the load that could cause a threaded pin to come unscrewed. Safety bolt pins are also a better choice when used in setups that don’t allow for particularly easy viewing/access to the pin for regular inspection purposes.