An apparatus (“chair”) for supporting one or more reinforcement bars or post-tension cables (“bars/cables”) in a concrete structure includes a base member having a centered opening, a pair of opposing first leg members extending upward from the base member at a first angle, a pair of opposing second leg members extending upward from the base member at a second angle, and a strap-shaped locking cradle. The strap-shaped locking cradle includes an arc-shaped receiving portion attached to the first and second leg members, a flexible portion suitable for wrapping over the bars/cables and a fastener to affix the flexible portion to the arc-shaped receiving portion or one of the first leg members such that transverse and vertical movement of the bars/cables is limited and longitudinal movement of the bars/cables is allowed.