I agree with the other Pfaffies here....the only application I don't use the IDT (built in walking foot) is for FMQ and embroidery. As K3n said, it's purpose it to alleviate shifting anywhere. However I do understand member's feelings about the bulkiness of one you have to attach as I have some for other machines and you don't have the choice of using whatever feet you want to use for various applications as we do with our Pfaffs. That is one of the main reasons we love our Pfaffs.