Abstract: Details for implementation of a Boundary Meshless Model (BMM) and a Meshless Plane Wave Decomposition Model (MPWD) calculating scattering coefficients of periodic structures with arbitrary shaped profiels are provided. BMM based on Mommertz's determination is applicable for finite samples. In contrast, numerical calculation is performed in a groove of one period in MPWD, which is applicable for samples with infinite surfaces. Random-incidence scattering coefficients of a sine-shaped sample and corresponding infinite sample are calculated using BMM and MPWD. Comparisons with measurements demonstrate that both models have good accuracy. Directional distributions of directional scattering coefficients are similar. At last, performances of the two models are discussed.