I am attaching a zip file containing the code and the executable for our project. 
The sketcher is now modified to include switching of crossings.

Please follow these guidelines to draw knots and the spanning or embedding surface:

0. Double click KnotSketcher.exe

1. Press the right mouse button to obtain a popup menu and click on "start a knot."

2. Left-click segment joints in the drawing window. -- DO NOT cross more than one
    existing line segments with any newly drawn segment.
 
3. Finish the knot by closing the contour; this is done by right-clicking to pop up the  menu. --
    DO NOT form any new crossings with this last closing segment.

4. To "switch" any crossing, just left-click on the crossing you want to change
    after the knot has been completely drawn and closed.

5. Write an SLF output file by right-clicking and using the menu.
    You may edit this output.slf file to change the background color, etc ...

-- 
Rahul Vinay Khardekar and Xiaorui Chen,
Mechanical Engineering Department
The University of California at Berkeley. 
5/25/2006