Procedures identifying velocity-coherent filamentary structures with the FoF algorithm in the Orion B region. The colored regions denote the filamentary structures identified from FoF with the criteria for spatial separation (﹩\sqrt{2}﹩ pixel size) and velocity difference V _diff (from 0.1–0.045 km s⁻¹) written on the bottom of the panels. The gray region in each panel is a continuously connected structure within the velocity criteria and the shades (darker regions) in the gray region indicate that there are multiple velocity components in the line of sight in the velocity-coherent structure. The insets in the panels denote C¹⁸O (1–0) spectra and their decomposed Gaussian components at a pixel point. The numbers in the insets indicate the velocity centroids of the Gaussian components at the start point of the arrow. The colors of the velocity centroid numbers and Gaussian-fit profiles correspond to the colors of the filamentary structures.