I am trying to draw a gear, basicly a tube with teeth along the perimeter. What I tried to do was draw two circles, then erased all of the vertices except for one segment. I then subdivided the outer segment a couple times, grabbed every other vertice, and pulled them towards the middle, creating the teeth. I then spun this 360, creating the top of my gear. My problem is, I am unable to get it to fill this face. I push shift-F and nothing. I can extrude this, but of course it is open on both ends. What am I doing wrong here, or is there an easier way to create a gear?