For most 3D machining tasks, you only need to select the model you want to machine once in the setup. The model and stock defined in the setup is used by the milling operations by default. Using the entire model for machining works as desired in most cases, and is also the recommended approach.
Occasionally, you might need to override the default model and select specific solids and faces. One example might be if you have patched some pockets with surfaces that only apply to specific operations.
You can override the setup model by enabling the Model group and then selecting the desired solids and faces.
Solid bodies are selected by default when you click on the model. If you want to select individual faces, you can do so by changing the :
Pressing X enables or disables face selection regardless of whether the selection filter dialog is shown.