Let's first look at the end of the drag wire coming through the end block on the front of the spar.  

Now, lets look at what Brent is doing with the hole saw.  He has previously drilled a hole in the spar at a pre marked point in the spar.  He is now inspecting where the hole saw is going to cut.  Next he will apply a doubler plate to the spar for increased strength to compensate for the strength loss of the hole that he just drilled.