Element Keypoints
Keypoints are regularly-spaced points in an element to which a tentative point will snap when the Snap Mode (or override) is set to Keypoint. The number of keypoints on each segment of a linear element (line, line string, or shape) is one greater than the Snap Lock Divisor setting. If Snap Lock Divisor is 2, keypoints are as shown in the figure below. The midpoint of a linear element is a keypoint only if the Snap Lock Divisor is an even number.