Autodesk Inventor iDoor Tutorial
Page 20 - The Panel Cutter Sketch - Continued
Leaving the sketches in the same isometric position, shut off the Panel
Profile sketch. Now activate the Panel Cutter sketch if need be, and draw
two line segments upwards starting at the far end of the longer line. They
can be as long as you want for now. When completed, grab the General Dimension 
tool
and add the Panel_Step parameter to the top segment.
Turn the visibility of the Panel Profile sketch back on and use the
Project Geometry 
tool to project the point shown below (the one that
controls the height of the panel) onto the Panel Cutter sketch. You can see
the point at the tip of the cursor way to the left in the image below.
(Note: the dimension visibility was turned off on the Panel Profile Sketch
for clarity),
Now you can shut the Panel Profile sketch off again, and re-orient the sketch as shown below...
...now draw a horizontal line from the projected point to somewhere shy of
the vertical lines on the left as shown in the left-hand picture below. as
always, look for the constraint Glyph, which in this case will be
Horizontal. After clicking to end the line, right click and select Done to
finish using the line tool. Now press the Ctrl key on your keyboard and
select the three lines shown in the image on the lower right, then click the
Construction 
icon located on the Parameters panel to change them to
construction geometry.
