It seems that my previous posts about fitting the back shoulder and neckline are quite popular so I will revisit the gaping back neckline issue I discussed in one of the fitting posts for Vogue 8664. Remember this?
As you can see, I corrected the gaping back neckline issue by adding a dart which eliminated the excess length in the neckline and addressed the contour of the shoulder blade. In most basic block patterns this back contour shaping is addressed by a shoulder dart which is usually placed at the middle of the shoulder seam and points toward the shoulder blade. The average width of this shoulder dart is between 1/2" and 3/4" but it will be larger for figures with more prominent shoulder blades.
If this dart is missing from your pattern, it is very likely that there will be gaping at the back neckline or the back armhole unless it's volume has been managed properly. Below are some dart manipulation exercises that will help you understand how to work with the back shoulder dart or gaping. Note that the dart is always rotated from the apex of the shoulder blade.
Use the armhole dart to establish a well fitted back yoke style.
For Andrea who wanted to know how to fix gaping without adding any darts, the method shown below can be used. If you want to eliminate the dart (or gaping) entirely, you will need to distribute the volume into the seams surrounding the shoulder blade as shown below. Distributing this volume creates ease in each of the seams so the gaping will be minimized and transformed into minimal ease on each of the seam lines it is transferred to.
In this case the back shoulder and armhole (which will be longer) will need to be eased into it's adjoining piece. Just a word of warning: If the dart or excess volume is very large, you are better off keeping the dart for better fit. The amount of ease in each seam should not exceed 1/4". If the dart is not manipulated correctly it will show as excess fullness in the armhole, neck, or shoulder and be very unflattering.
As always, if you have any questions, post a comment!