A safety apparatus is capable of tensioning a horizontal lifeline while providing an adjustable shock absorber and a gauge or indicator for indicating the amount of tension on the lifeline. A housing is adapted to be secured to an anchor point through an anchoring line. The free end of a horizontal lifeline passes over a pulley within the housing and around a number of rollers which are adapted to maintain the lifeline in secure contact with the pulley. A lever is utilized to rotate the pulley in order to tension the lifeline. The lever, however, is interconnected to the pulley through an adjustable disk brake which can be preset to a desired force. When the tension on the lifeline reaches its desired level, the brake slips and the lever can freely rotate. A second series of disk brakes connected to the pulley function as a shock absorber. In the event of a fall, the initial force on the horizontal lifeline exceeds the braking force of the shock absorber brakes and the pulley can rotate through a limited number of turns. Eventually, however, the shock absorber brake slows the fall and eventually stops the same. The amount of tension on the shock absorber brake can also be adjusted to thereby control the amount of shock being absorbed. An additional brake mechanism prevents the lifeline from freely being drawn from the housing in the event of a complete failure of the mechanism thereof.