Newbie question

I am following a tutorial in a book but one step is confusing me.
I am creating a propeller blade by the way. I created a closed poly line shape then selected it and applied an extrude modifier and set the thickness to 1. The poly line thickens but the inside is still hollow. The tutorial then says render the blade and I cannot see any modifier to do this? Will this create my solid propeller blade? Any help and steps would be appreciated.

Fixed. Not sure what happened but the polyline join I applied wasn't valid. I redrew the shape in one go and it worked this second time. Not always possible to confirm when you have successfully joined two polylines to use for extruding 3D.