Midpoint

Selection prerequisites: One or more segments.

Constructs a point at the midpoint of each selected segment. As a segment gets longer or shorter (through dragging an endpoint, for example), the midpoint moves accordingly.

The keyboard shortcut for Midpoint is Ctrl+M (Windows) or z+M (Mac).

See also
Points
Segments, Rays, and Lines
Object Attributes
Using the Construct Menu
Object Relationships: Parents and Children
Selecting and Deselecting Objects
Dragging Objects