This bad boy has a little metal guide in the center that runs down the seam. I've been doing a lot of topstitching on my clothing and this thing just opened up new doors for accuracy.
Using a standard presser foot, I had to eyeball the seam and the center mark, which means I may get a little drunk driver and go off center, particularly if I'm going fast. The guide done the center makes sure you stay on the seam, perfectly straight.
So far, I've used it for the following applications:
Stitch in the Ditch
This technique is good for when you don't want a visible line of stitching but you need to follow an existing seam. On this example (oh look, more Camo), I'm stitching in the ditch to close the collar. I'm following the existing seam line and stitching right over it and catching the collar on the back side to close it up. I can't see the new stitches, which is the point.
Joining Edges
This guy makes my thumbhole cuffs much easier! When I butt the seams together the pressure from the foot holds them together in the guide and I can zigzag right over them to attach them together.Topstitching
This is probably my favorite use yet. I've found that I like the finished look of topstitching on either side of a seam. Until now, I've been doing it with my standard foot, which means I'm eyeballing it and sometimes not exactly centered. This foot allows me to put the guide in the ditch, offset my needle and I've got a nice, straight stitch!
Summary
The only caution I would share is to be careful crossing seams. The guide wants to follow the seam and when you cross another seam, it sometimes gets caught, so I go really slow to make sure I don't snap off the guide or bend it.Overall this thing is awesome!