Activate the command: Model
Clipping Planes.
Using this dialog box, you can specify slice planes so that you can view the interior of your model.
You can use any combination of the three global planes and a user defined plane to slice your model.
Enable: Activating this check box will cut your model using the respective plane going through the origin. The part of the model on the negative side of the plane will be hidden. Moving the slider bar to the left will move the plane to the negative side of the origin. Moving the slider bar to the right will move the plane to the positive side of the origin.
Invert: Activating this check box will cause the part of the model on the positive side to be hidden.
For the Custom plane, specify the components of the vector that is normal to the plane using the X:, Y:, and Z: input fields. To specify the normal direction, activate the Enable box, change the values, deactivate (clear) Enable, and then activate Enable again to use the new input values.