What style of modelling are you going for , box, spline, poly by poly? I assume your 2d planes are polygon objects so I guess your next step would be to extrude along x axis several times adjusting the shape of each extrusion as you go. But like Cryptojoe says it will depend on your app and preferred modelling style. If I was modelling a car I'd probably try and box model it (and make a real mess I'm sure LOL!)Splines are very popular for car modelling and I believe Nurbs are supposed to be the best of all. - Baz