Butforthisstrangelookingshackle, theshackleis a combinationofsteelandzincalloycastings, and I believetheideaistopreventboltcutteraccesstothisthinportionoftheshackle.
Themostcommonplacethat I seetheseissecuringthelatchof a trailercoupler, butonlyfitsmostcouplersifyoufirstremovethisshacklesleeve.