I'm a longarm quilter and have had a number of clients bring sheets to me to use for backings for their quilt. Though I've read many negative posts about sheets as backings but I've never had any problem with them at all. These quilts I was brought were not of a high thread count, probably purchased at Walmart or Marden's (local salvage store). Maybe a 600 thread count sheet would be problematic, I have no idea but so far so good for me.