A grate bar (for forming a plank of a conveyor grate for transporting bulk material) includes at least an up-facing surface for supporting bulk material, a down-facing surface for supporting the grate bar on at least one grate bar rest, front end and rear-end sides, first and second profiled narrow sides. The first and second profiled narrow sides are complementary to one another and form a moving gap therebetween if and/or when the first profiled narrow side of the chosen grate bar is positioned adjacent to the second profiled narrow side of a neighboring grate bar (that is identical to the chosen grate bar at least with respect to the profile of the second profiled narrow side). The grate bar can be easily replaced if a front edge between the up-facing surface and the front-end side has a front edge curvature, a rear edge between the up-facing surface and the rear-end side has a rear edge curvature and the rear edge curvature is complementary to the front edge curvature.