Abstract: A security locking bolt for flanging "Christmas tree" installations, valves and other equipment to a pipeline header or a pipeline, which includes a bolt body having a partially threaded bore and a security bolt head integrally provided on one end and a cooperating locking head secured to the opposite end of the bolt body by means of an internally-seated locking bolt which threadably cooperates with the internal threads in the bolt body. In a preferred embodiment a roller bearing is also provided in the bolt body bore and an end cap closes the locking bolt access opening in the locking head. In another preferred embodiment of the invention a grease fitting is threadably inserted in the security bolt head and longitudinal apertures are provided in the roller bearing and the locking bolt in order to provide a means for inserting grease into the threaded bore and removing the end cap situated in the locking head, by application of pressure.