When the Recognize Connector Points preference is enabled, PathScribe can recognize and work with connector points: points that act as transitions between straight segments and curved segments.
A connector point:
Can be either a smooth or corner point, but not an endpoint of an open path;
Must have a single handle that faces directly away from another point (the base point);
Must be adjacent (on its non-handle side) to a segment with no handles
Additionally, for PathScribe to recognize a point as a connector, its handle must be lined up with the straight segment. The amount that its handle can be off and still qualify as a connector is called the angle threshold. It has a default value is 5° but can be set in the preferences dialog.
PathScribe Recognize a point as a connector
Hovering the cursor over a path will identify all of the path’s recognized connector points by drawing a small “C” above them. The color of the “C” indicates whether a connector is within the angle threshold but not perfectly lined up (gray) or aligned precisely (red):
PathScribe connector point indicator
You can use the PathScribe panel to align all recognized connector points on selected paths. Also, nearly all clicks and drags with the PathScribe tool on a connector point, its handle, the segments next to it, or the points adjacent to it, will automatically align (if not already), and keep aligned, the connector point’s handle. (Exceptions include Multi-Handle drags and Shift+Option/Alt-clicks
that retract or extend new handles.) When a connector point is being automatically aligned during an edit, a red “C” will appear above it. If the edit removes the connector’s points handle (such as dragging its handle back until it is of zero length), the “C” will disappear.
Since other Illustrator tools will not see connector points any differently from non-connector points, any geometry edits other than those that affect the entire path (such as moving, rotating, and scaling) should only be done using the PathScribe tool, or any connector point’s handles may be disturbed.