Click the Solid wizard
button and select Cut with parting surface from the Solid Modifier category or Select the Cut with parting surface
button from the Solid toolbar.
Select the name of the solid in the Cut this solid drop-down list or click the Select solid
button and pick the solid in the graphics window.
Select the name of the surface in the Surface drop-down list and click the
button or click the Select surface
button and pick the surface in the graphics window.
If you have additional surfaces to cut with, repeat step 3. Remember that the surfaces must have common edge curves that allow them to be stitched together.
If you wish to create a solid for both sides, check the Keep both sides checkbox.
Click the Preview to preview the cut. The result will be shown in thick blue lines. If you want to cut on the other side of the surface(s), click on the surface name and click the Reverse
arrow.
Click Finish or OK.