Originally Posted by JustAbitCrazy

Some machines have upper feed dogs, too, like a built-in walking foot. For many years Pfaff machines were the only machines to have them, I'm sure it was because of their patent. Now other machines have them: Janome, Babylock, to name two that I know of for sure. On a Pfaff machine it is called their "IDT" system, and it's awesome because the top fabric feeds through the machine at the same rate as the lower fabric, making it so much easier to match points. Think of a long seam, like a pant seam, and how you end up with an inch of "extra" top fabric when you finish the seam. That doesn't happen with upper and lower feed dogs, which are coordinated to work in unison. You can use a walking foot on many machines to accomplish the same thing, but they are sometimes big clunky pieces, hard to see around. The Pfaff IDT foot is narrow and unobtrusive, you don't even realize it's there. It's a narrow black piece that drops down behind the regular foot and glides into a groove on the underside of many Pfaff feet, not just the basic foot, so it can be used with most of the specialty feet as well as the basic foot, something you can't do with a big walking foot. You'd think I sell Pfaff machines, lol, but I'm just their number one fan, I guess.