Abstract: A security seal device is shown formed of plastic material generally in the shape of two hollow half cylinders connected together by a longitudinally extending living hinge and having apertured end faces. Spaced, opposed lips are formed in laterally extending shelves attached to each half and a locking pin is received between the lips and projections formed in the pin received in detents formed in the lips to lock the two halves together. The device is used by placing a joint formed between first and second members within one of the halves with the first and second members placed through respective end face apertures. The other half is then pivoted to close the cylinder and the locking pin is inserted. The device can then be reopened only through physical damage by breaking the seal.