Mesh overlap.
 

Hi; I am simulating in a bend, i need to use different mesh patterns. 1) i try to create a cylindrical toroid, then in the center i create another rectangular toroid, in 3-D. How do i get rid of the cylindrical mesh in the region of the rectangular one. The Star mesh n geometry check shows no errors, but i can see two meshes on top of each other instead of a merged. (i also tried to use the merge command) 2) i tried to extrude it by creating a 2-D square in a circle. It does not let me select more than 8 points for creating a block. Now i cannot mesh it without creating a block?....I need some hints on both of the above. Thanks in advance.