90 tbird sc crank sensor help!

im trying to change my crank sensor!the book is hard to understand !it says rotate the crankshaft by hand to position the metal vane of the shutter outside of the sensor air gap!ok whats the metal vane and whats a shutter?also how inportant is it to set the gap when replacing the sensor? also how do you do this without the tool!please explain this to me in english cause i really dont understand the book!thanks!:uhoh:

They have a toothed ring like a bicycle. You use a brass feeler gage and set the gap between the top of the tooth and the bottom of the sensor. Its is magnetic. Depending on the room you can mark the depth the same as the old one. Rotate by hand and make sure nothing is rubbing.