Step 4: Marking and drilling
So now that the aluminum is bent, it's time to drill some holes for the switch and the strain relief zip ties. The strain relief ties are important, because they will prevent the cord from pulling away from the device over time.
First, you'll need to use a center punch to mark the center between bends one and two.
Next, use a center punch to mark four holes for the strain relief zip ties to go through. I used graph paper to center and square the holes. (It wasn't that accurate, but it did the job. You may want to spend more time laying out these points.)
Time to drill!
First drill the 15/64" hole for the switch between the 1st and 2nd bends.
Then drill the four 1/8" holes for the zip ties.
When you are done it should look something like the last picture in this step.