HI, I never model in CAD but I was asked to do something quick: so i used the rectangle tool and i changed the thickness of it to add height but I had no idea that this doesn't automatically add the top to the object. Is there a quick way to fix this: i have hundreds of rectangles and i really don't want to draw a 3d face on each one of them.Thanks!

Have you tried to extrude the face of your rectangle(s)?
(extrude from solids toolbar).

HiIf you are using 2008 and above,hold down ctrl+alt keys.move the cursor inside the rectangular area (or any closed area).the contour gets highlighted (provided the SETVAR variable HIGHLIGHT is 1)click the mouse button and key in the desired thickness value.This may be a faster method for you.umesh