Continuing with the "Fitting Dresses" booklet from the U.S. Department of Agriculture.
Fitting The Hips
When the skirt fits correctly, the center front and center back hang straight down without swinging out in the front or back. The side seams also hand straight down, giving the appearance of continuing the underarm seams of the waist. The crosswise grain of the goods is parallel to the floor. The space between the waist and the hips is fitted smoothly but not tightly. The only exceptions to these rules are skirts with special styling.
The first step in fitting a skirt is to see that the crosswise grain of the goods is in a straight line around the hip line. If it is not, raise or lower the waistline a the points where the grain is out of line or rip the skirt at the seams and raise or lower the sides as necessary.
A well-fitting skirt of any kind, plain or fancy, does not draw or pull when the wearer is sitting or standing. When the fitting is complete, ask the wearer to sit and also to move around naturally to see if the skirt will be comfortable and will hang gracefully when worn.
Side seams of skirt are crooked and puckered. The dress may be poorly sewed together. Careless joining of the side seams (one seam edge eased too much onto the other), crooked sewing, or too tight sewing machine tension will cause puckered seams.
Restitch a straight seam if stitching is crooked or loosen any tight sections in the seam. Otherwise, open the side seams, pin, and bast, matching the grain of the cloth at the hip line. Avoid drawing the basting thread too tight. Try on. If satisfactory, stitch carefully.
Skirt draws across hips and tends to ride up. The skirt is too small. If the side seams are wide enough, let them out until there is no stain across the hips. Keep the side seams hanging straight. If there is not sufficient side allowance for this and the skirt is long enough raise the skirt at the waistline and refit it. It may be necessary to face the hem.
Skirt cups in the back and the side seams swing forward. The back of the skirt may be too long between the waist and the hip -- thus allowing the grain of the goods to drop at the hip line. This causes the side seams to swing forward (see figure 24, A).
Raise the skirt at the back waistline until the grain of the goods is straight across the hips (figure 24, B). If this makes extra fullness at the waistline, take it out in two darts. Trim off the top of the skirt in the back, at the waistline.
If the dress is one-piece, without a waistline seam, rip the underarm seams, raise the back at the shoulders, then recut the back neck and armhole lines.
Lower edge of skirt swings out in back. The side seams swing back (see figure 25, A). This may be because the figure has a sway-back and large hips. Extra length is therefore needed in the back of the skirt. Sometimes the crosswise grain of the goods is pulled up out of line. In some cases, the flare of the skirt in the back may be too pronounced for the type of cloth used.
Rip the back of the skirt from the waistline, letting out any extra seam allowance so as to drop the back of the skirt and thus straighten the crosswise grain.
If the seam allowance is too small to let out the seam, rip the skirt and waist apart, and lift the front and side front gores of the skirt until the cross wise grain of the goods is straight all around the hip line (figure 25, B). Mark a new waistline on the skirt, pin, baste, and try on again before stitching on the machine.
When the grain of the goods is straight at the hip line and the trouble seems to be only in the flare of the skirt, it may be eased out some at the seams.
Crosswise folds across the back between waist and hips. The skirt may be too tight at the hips or the figure may have a sway-back.
If the skirt is too tight, rip the side seams (if necessary, also the back gore seams) and let the skirt drop into an easy position. Pin and baste.
If the side seams are too narrow to let out, raise the skirt at the back so as to take out the fold, keeping the crosswise grain of the goods straight across the back hip line (Figure 24, B). Trim off the extra goods at the waist. If there is extra fullness at the waistline, take it up in the seams or, if necessary, in back skirt darts.