A rod-bed assembly has a holder (30) and an insert (20) removably and insertably supported in a groove (31) of the holder (30), the rod-bed assembly being for a rod (10) rotatably supported in a recess (21) on a front side of the insert (20). Longitudinal bending of the holder (30) in a cross-direction is under 0.5%, advantageously under 0.35%, of the longitudinal distance between two profiling loading points of the holder (30).