A method of assembling a load center featuring a dielectric barrier that securely retains a plug-on neutral rail without requiring any fasteners. The dielectric barrier and the rail are installed in the same Z-axis direction, which is orthogonal to a rear wall of an enclosure into which the load center is installed. Retention features in the dielectric barrier can create a snap-fit connection between the rail and the barrier, or the barrier can feature a support feature onto which the rail snaps as the rail is installed relative to the dielectric barrier in the Z-axis direction. The snap fit connections eliminate the need for any fasteners, and together with the Z-axis assembly, the assembly process is simplified and accelerated and the possibility of assembly error is reduced or eliminated.