A hollow metallic rectangular waveguide conveys ultra-high frequency electromagnetic waves through repeated total internal boundary reflections off highly conductive metal walls. In the dominant TE₁₀ mode (Transverse Electric), the longitudinal electric field vanishes (E_z = 0) while the transverse electric field E_y is sinusoidal across the broad wall dimension 'a'. Propagation occurs only at frequencies exceeding the cutoff frequency f_c = c / (2a), with guided waves traveling with guide wavelength λ_g > λ₀ and superluminal phase velocity v_p > c.