My Sil routinely puts fitteds on with out a cover, she has put them on backwards. Even a pocket with no insert.
Worst part is she lives with me. She has used them since the twins were born. I have taught her the ins and outs of all of them more than once. I even teach classes on how to CD she just can't learn how to do it. It's beyond me lol. At least when my mil is in town she has no problems when it comes to pf's and such, because she CD'd all of her kids.