This is an awesome thing! It's a knitted swiffer cover. I got this pattern from a wonderful member of my monthly dishcloth group. Her name is Sarah and she shares the pattern on her blog. It can be found here http://www.sheepofadifferentcolor.com/swiffercoverknitted.htm
It's so much better than the store bought sheets. I'm making another one so that I always have one clean. You just toss them in the washer and dryer and they're ready to use again. And I can use up my leftover cotton yarn...they don't even have to match. She's such a smart woman.
Here's a photo of the bottom....this one is actually pretty, I think.
My sister has already put in her "order" for two. And I am going to adjust the pattern so that I can make a couple for my Swiffer Wet Jet. I like the Swiffer fine but my Wet Jet is my favorite. I absolutely love that thing. We'll see how it works with that one as well. Would be a lot cheaper than buying the refill sheets in the store. Thanks Sarah! I'm so glad you shared the pattern with us.