Bryster's got the idea... Although it looks like some of your parts aren't at "0" on the X and Y. Gotta keep it all lined up, if you want symmetry... Fran, the spheres are negative spheres, just making some little semisphere pits as they carve into the positive shapes. The cylinders towards the top are just for fun, too! I made this real quick to illustrate the same thing Bryster was doing... Kinda got carried away, perhaps I'll use this for something else one day. A simple screenshot of the wireframe overlaying the render.