The oil casing bull plug is a robust, solid cylindrical device used to permanently or temporarily seal the end of a casing string. Typically made from high-grade steel, it features robust threads for a secure, pressure-tight connection. Its primary function is to isolate lower zones during well completion, testing, or workover operations. It also serves as a protective cap during transportation and handling, preventing damage and contamination to the casing threads, thereby ensuring well integrity and operational safety.