Steel Screw Pin Anchor Shackles - these shackles have a thread protected end and are able to hold 5 times the working load limit. Steel Bolt and Nut Anchor Shackles - made from alloy steel that is heat treated and tempered. These shackles are fastened with a thread as well but it also uses a nut to secure the wire rope. Both of these tools are used to clamp the loose ends of a wire rope after the rope has been looped back.