+ :title [choosing drill bit]
+ (p [choosing the right drill bit depends on what job you are doing.
+ right now, we are making holes for screws to hold the
+ arduino to the deck.
+ this means the hole needs to be big enough for the
+ screw body to fit through.
+ we want the screw to stay put once it's in place.
+ we also want the drill bit to be smaller than the
+ diameter of the thread.
+ the screw was chosen so that the hole on the arduino
+ was bigger than the body and smaller than the thread.
+ we will choose the biggest drill bit that fits through
+ the hole on the arduino.])
+ (p [here's a diagram of a screw]
+ (figure :legend "screw" (image :file "arduino-to-deck/screw.png"))))