What rhymes with perpendicular direction?
per·pen·dic·u·lar di·rec·tion

In the march of a line, is the direction at right angles to the line which each man should take in a direct movement to the front. Without the strictest attention is paid to this essential principle in all movements, the greatest irregularity, and ultimately the greatest confusion, must ensue. Perpendicular and parallel movements constitute, indeed, the whole system of good marching. When several columns, divisions, or companies advance, the lines and directions of marching must be strictly perpendicular and parallel to each other, otherwise the distance will be lost, and the ultimate object of forming a correct line must be defeated.

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