they are cut with pinking shears to keep them from raveling...
manufacturers really can not win no matter how hard they try. they cut pre-cuts with straight edges, sell a few and people complain...they ravel, they are not a consistant size. i washed them they frayed horribly now my 2 1/2" strips are only 2"....
so, they started pinking the edges...now they don't fray anymore but the complaints sure didn't end. now people complain about that pinked edge.
well, they aren't raveling apart anymore...and i agree with the manufacturers...sure wish someone would just accept what is.