A comparison between a kinematic analysis of the fractional-order LEED-pattern symmetries of the Si(111) 7×7 structure and experimental data is presented. The surface model comprises a rippling of the first two double layers so as to produce interference in the coherent scattering from this distortion. The ripple deformation is small. It is treated as a perturbation in the analysis. Thus, the surface is nearly ideally terminated; there are no vacancies or adatoms in the model. Triagonal symmetry reversals are observed in the LEED patterns at about 20-V intervals and are also computed theoretically.