I-beam-attachable lifeline system, including methods and apparatus, for worker safety. In some embodiments, the system may comprise a frame structure including upright columns and horizontal I-beams. The system also may comprise a pair of fittings connected to a horizontally-spaced pair of the I-beams. Each fitting may have a first hook component and a second hook component received on respective opposite edge regions of a flange of an I-beam of the pair of I-beams and attached to one another with a fastener such that the fitting spans the flange transversely and is supported by the I-beam. The system further may comprise a cable having opposite ends connected to the pair of fittings.