This weeks little helper is mainly needed for stretchy fabrics - the twin needle! Not only does it two nice lines next to each other, as the back with the bobbin thread is zigzag, the hems or seams stay elastic!
What is it good for?
Well, doing twin stitches, duh!
Well, as I said above, you can do elastic hems with them. But you can also use them to do double seam on jeans - with a needle for wovens of course! Or decorative stitches with a twin needle, but beware: Only in the width of your presser foot.
By the way, if you have problems with the fabric accumulating in the middle between the two seams, you can either try reducing the opper fabric tension, iron on some interfacing under the seam or iron the sh*t out of it after sewing. All reduce the "wall formation"!
How much does it cost?
Depending on where you buy them, you pay between 50 cents (hah! ^^) or 4 Euro. They are not very expensive and really usefull!
Who needs it?
I think most people do, but if you never work with jersey and have no intention for using them for decoration you don't. Or if you own a coverlock machine. If that is the case, I might be your new best friend and come over to visit you with a bunch of unhemmed shirts! ;)