Based on the answers provided, the following corrections need to be made to the 3D object:

1. Modify the structure to resemble a workbench. This should include a flat surface supported by legs.
2. Ensure the length of the rectangle is approximately three times its width. This should be clear from the design.
3. Make sure the depth of the surface is equal to the width of the rectangle. This should be clear from the design.
4. Provide a clear indication that the inside of the rectangle is hollow.
5. The legs of the workbench should be centered and perpendicular to the upper surface.
6. Ensure the length of each leg is approximately three times its width. This should be clear from the design.
7. Include a rod connecting the bottom of the left and right leg.
8. Make sure the diameter of the rod is marginally less than the width of each leg. This should be clear from the design.