We all like Fully-Defined sketches. There’s no room for ambiguity. The sketch and resulting features are more stable. Rebuild times are improved. SolidWorks likes fully-defined sketches as well. And, when you’re editing a sketch, SolidWorks is kind enough to tell you when your sketch is fully defined. However, sometimes it will tell you the sketch is fully defined when it’s “fully defined enough,” meaning there may be under defined bits in it. I am, of course, referring to the endpoints of construction lines. However, I’ve recently learned that there are other instances when a “fully defined” sketch is not so.