It is easy to identify through the naked eye.
Plain weave:
There is no difference between the front and the back in actual use.
Twill weave:
Single-faced twill: For example, twill and single-faced khaki, the front lines are clearly visible and the reverse side is blurred.
Double-sided twill: such as gabardine, double-sided khaki, enamel, etc., the front and back lines are basically the same, but the opposite direction. The front grain of the single yarn fabric is inclined from the left to the right; the texture of the half-line fabric or the full-line fabric is inclined from the left to the right.