A circuit board chassis and a method for assembling a backplane and a circuit board into the circuit board chassis include an aperture within at least one sidewall of the circuit board chassis. The backplane is inserted and assembled into the circuit board chassis through the aperture (that may include a counter-opposed pair of backplane insertion and assembly slots) in a first direction, and a circuit board is inserted and assembled into the circuit board chassis and the backplane in a second direction perpendicular to the first direction. By inserting and assembling the backplane into the aperture and slots, rather than assembling the backplane as an external surface component of the circuit board chassis, the embodiments provide for ease of replacement of the backplane and circuit board under space constrained limitations. The resulting embodiments also provide enhanced rigidity and enhanced thermal dissipation within the circuit board chassis.