Sechushin and Wakinui
“Sechushin (middle of the back) and Wakinui (side seam) are terms frequently used at Kimono making and wearing. Sechusin is the straight stitch from the top to bottom on the back of a Kimono. To wear a Kimono beautifully, the stitch should looks straight in the middle of your back. If the size of the Kimono does not fit you, the stitch under the lower back would not appear in the middle of your body, but this is acceptable. However, in this case, you still have to make sure that the stitch is not on a slant.
Wakinui is a term used for western clothing as well, and means the seams between the front and back bodies of a garment. Above the lower back, Wakinui should fit to the side of wearer’s body, but under the lower back, they do not have to be exactly on the line. When you make a Kimono from a cloth, there would be some surplus width on the cloth, and it should be hidden inside as a margin for a seam. Because of the hidden cloth, a small Kimono often can be made wider, by undoing Wakinui and sewing it again. A large Kimono also can be made smaller in the same way. Although it is difficult to resizing an authentic Kimono, some resize Yukata (casual summer Kimono) by themselves.