Second, get two 3/4" PVC pipe caps and some JB Weld. Drill two holes near the sides of the end of each cap, just slightly bigger than the cable. Take one end of the cable and run in in to the open end of a cap, make a loop, and run it back through the second hole. Adjust the cable end so it is not protruding past the end of the cap. Do the same for the other cap, fill them both with JB Weld and let them cure. What you have is a piece of cable with a knob on each end that will keep somebody from pulling it through the door opening.
Actually, you are done with the cable part of the Instructable unless you want to dip the ends in Plasti Dip rubber tool handle coating to make it look more professional.