The difference between one letter or two letters; writing with a "SHINUI" (not the usual manner). One letter on top of another letter.
various examples of double knots and single knots at the end of a bag.
Understanding the Difference Between ממצא חפציך (Mimtzo Cheftzecha), דבר דבר (Dabair Davar), and הכנה (Hachana);