Need a complicated shape or adherence to some pre-defined geometry?
Here is a simple demonstration of how REPLACE can be used to easily achieve the desired, though complex results.
Image 1 shows the original model. The protrusion on the back with the flat sides really should conform to 3 of the sides of the previous geometry. To accomplish this, the protrusion is EXTRUDED / BOTH SIDES / UP TO SURFACE to accomplish the shape in Image 1. (This accomplishes adherence to two of the faces, but as can be seen, the third might be a problem.)
|Next make a surface copy, ( FEATURE / CREATE / SURFACE / NEW / COPY ) shown as the Yellow shaded area in Image 2.|
|Finally, use FEATURE / CREATE / SOLID / TWEAK / REPLACE and pick the surface of the solid to be replaced, then pick the newly created surface (the one in Yellow above) as the replacement surface. The resulting contour is highlighted in green below.|
|There you have it, the result is shown in images 3 and 4. For more information on using REPLACE, consult the Pro/E documentation.|