A system for securing a life-line around the outside of a structure, e.g., the wheelhouse of a boat, includes attachment devices for the life-line at intermediate positions therealong (particularly at corner parts of the structure) which allow a hook of a safety line attached for sliding movement to the life-line, to pass those attachment points. In one embodiment each attachment device comprises a recessed wheel and a slipper member located to embrace tip portions of the wheel projections to be held thereby while allowing rotation of the wheel relative to the slipper member. In this way the slipper member guides the line in an arcuate path around a peripheral part of the wheelhouse to allow a hook engaged for sliding movement along the life-line to traverse the attachment point by engaging in a recess in the wheel which then rotates relative to the slipper member to pass the hook through the attachment device.