The idiom "鳞次栉比" is formed by combining two parallel similes: "鳞次" (meaning "like fish scales in sequence") and "栉比" (meaning "like comb teeth arranged closely"). The character "鳞" (scale) and "栉" (comb) provide concrete objects for comparison, while "次" (order) and "比" (arrange) describe their sequential and tight alignment, resulting in a compound that visually depicts dense, orderly placement.