Things to Note when Modeling Opening Trims

You should take the following things into consideration when modeling opening trims:

The origin of the bottom trim must be at the lower left corner of the opening.
The origin of the top trim must be at the upper left corner of the opening.
The origin of the side trim must be at the bottom right corner of the opening (automatically mirrored when used as the left-side trim).
LENGTH is the length variable, which is either the width or the height of the opening, depending on the trim type.
The end overlap variables for the side trim are OVL_SILL and OVL_TOP, and for the other trims OVL_LEFT and OVL_RIGHT.
The width variable of the trim is WIDTH and the depth variable DEPTH.
The trim may not move in relation to the origin when the dimensions change.
The material category of the trim is TRIM.

You can define a cutting shape for a trim to cut a wall in the building model.

Create the trim as an assembly model.
Create a part of its own for the cutting shape.
When you extrude the sketch defining the shape, select the check box Tool in the extrusion properties.
The program highlights the cutting shape in color.

You can show and hide the machining features in the model (also in the building model) by pressing the M key.