Edge polygon
The Edge Polygon 
tool is used to draw an
edge polygon by specifying the first two vertices.
The Edge Polygon tool is used to construct a polygon on a given edge. The two clicks define two consecutive vertices of the polygon, in the counterclockwise direction, and the rest of the polygon is constructed correspondingly.
Using the mouse
The first click of the left mouse button sets the first vertex of the polygon.
The second click sets the next vertex of the polygon.
Here is an example, where a hexagon is constructed on the top right edge of the rectangle.
Using the keyboard
Enter the Number of sides, Start point and End point into the input boxes, then press Enter to draw the Edge polygon.