Surfaces are selected

Surface is trimmed.

In this example, the smaller surface will be trimmed.

Surface is trimmed.

Input

Action

with plane: surfs selector

Pick the surface to trim.

When trim with planes is active, a fill cuts mode is available. This mode is turned off by default. Select the fill cuts check box to turn it on.

vector selector

Select the vector coordinates.

fill cuts

Activates a special mode of surface trimming. A virtual trimmer surface is created and used to calculate and create new edges on selected surfaces. An attempt is made to insert pieces of this trimmer surface into the body when trimming of the trimmer itself by selected surfaces creates closed loops and thus cuts off those pieces. This is used to simulate solid trimming in cases when you cannot, or do not want to, create solids, but still wants to make solid-like cuts. 
 
This mode is not intended when selected surfaces are solid surfaces themselves. When attempting to insert pieces of a trimmer surface into a solid body, you may also need to manually select other surfaces in order to avoid topologically invalid results. If you do not make this selection completely correctly, the expected result will be undefined. 

with surfs: surfs selector

Pick the surface to trim.

trim both

Activate this check to have both surfaces trim each other.

extend trimmer

When this option is active, the trimming operation extends beyond the boundaries of the nodes, or lines that you used to define it.

Only available when trim both is inactive.

self-intersecting surfs: surfs selector

Pick the surface to trim. Every selected surface is trimmed at their intersections with each other.  This is very similar to using the trim both option when trimming with surfs, except that you simply select a single mass of surfaces and HyperMesh sorts them all out and trims each one whenever it intersects any other selected surface.

This feature is useful when dealing with cases such as a grid of intersecting surfaces.  Using the intersecting surfaces trim option allows you to separate all of the intersecting surfaces into multiple smaller surfaces with a single action, instead of having to trim them in pairs.