debjayne:
Just use a Fill that matches the fill of the walls and draw it to cover the line(s). You may need to use the
Display Order (Bring Forward, Move Backward) to get the fill to cover the walls. This is a 2D solution, it has no effect on the 3D model. The Patch solution is more complex, involving the creation of a custom library part to do this job, but the Patch can more easily be reused for multiple identical instances.
David