If you’ve ever worked with double fold, pre packaged binding, you’ll find that it can be a bit temperamental in the stitching process. However, storebaught double fold binding has a clever (and subtle) design element that will save you some headache in the machine stitching process.
If you take a closer look at a pre-packaged double fold binding, you will notice that one of the folded layers is narrower than the other. While this may look like a folding error, the small difference in length is quite intentional.
When aligning the double fold binding to encase a fabric edge, the longer layer is placed underneath, while the shorter one naturally corresponds to the top of the application. In the machine stitching process, the longer layer underneath will provide enough excess so that if the binding moves out of alignment, you can still catch the bottom layer underneath. Binding tends to shift out of alignment quite easily in the machine stitch thing process and while you have optimal control of the the top binding fold, the bottom one is more difficult to control this the longer layer at the bottom provides more room for error