These are linear anchoring devices used in Fall Arrest and Fall Protection Systems, which allow workers to move along the whole length of the Fall Protection System, usually without needing to disconnect and fixing points of the anchorage.
It is normally essential to include energy (or shock) absorbers within HLL in your Fall Arrest System in addition to those within the workers’ PPE. Without such absorbers, the horizontal lifeline cannot deform significantly when arresting the fall. Because of the geometry of pulling across the horizontal lifeline, this in turn results in large resolved forces being generated within the anchor system, sufficient to cause failure of the anchorage. This can occur even with energy absorbers being included in the PPE of the worker.