Trims one or more surfaces along the input element you define.
You can use a curve, reference plane, or another surface as the input element.
If using curves,
They must lie on the surface you are trimming; use the Project Curve command to project the curve onto the surface first.
Closed curves that do not completely lie on the surface are not supported.
If using a curve or surface as the trimming element:
If the curve or surface boundary does not extend to the edges of the target surface , the trim boundary element is extended linearly and tangent to the input element.
For example, surface (B) is used to trim surface (A). Since surface (B) does not extend to the edges of surface (A), linear extensions are added to the trim boundary element (C). The input element you select as the trimming tool (B) is not modified.
When you use a curve as a trimming element and it does not lie on the surface you want to trim, you can use the Project Curve command to project the curve onto the surface first. Closed curves that do not completely lie on the surface are not supported.