A sock anchor unit (10) comprises an inner longitudinal hollow spine (12), an outer fabric sleeve (14) arranged to envelop the outside surface of the inner hollow spine (12) such that a gap is defined between the outside surface of the inner hollow spine (12) and an inner surface of the outer fabric sleeve (14) and a plurality of elongated reinforcing members (22), wherein each elongated reinforcing member (22) extends longitudinally within the gap.The inner hollow spine (12) comprises at least one substantially laterally extending opening from inside to outside of the inner hollow spine (12). The opening allows cementitious fluid which is pumped into the anchor unit to fill the gap between the hollow spine (12) and outer fabric sleeve.A fastening member (28, 32) is provided on each end of the sock anchor unit (10). Both fastening members (28, 32) are compatible with each other and each fastening member (28, 32) is configured such that a trailing end of a first sock anchor unit (10) is attachable to a leading end of a second sock anchor unit (10) thereby facilitating creating a multiple piece sock anchor system of a desired length.