The bolt type anchor shackle (or bolt type bow shackle) is a shackle with rounded “O” shape look and a bolt/nut/pin combination. The larger loop reduces an anchor shackle’s strength, but it is able to efficiently handle a larger strap.
Screw pin anchor shackle has a larger bow than that of a U shackle; and so it has a larger surface area for riggings such as slings and crane hooks that simply would not fit in the loop of a regular U shackle.
Screw pin anchor shackle links different equipment together as they can be attached and detached easily.
A screw pin chain shackle is a U-shaped shackle secured with a screw pin. It connects lifting components. The loop in chain shackles is narrower than the one in anchor shackles. The narrow loop is designed to support a heavier load than a similar size anchor shackle.