Use :CC2BREAK: to remove the parts of them you don't need. Remember you can use the :CC2MODINT: modifier to get the exact points where they cross.

Breaking a polygon WILL turn it into a line, but just continue working with the line until it is correct, and then you can turn it pack into a poly when done by right clicking :CC2EXPLODE: and picking Path to Poly. If you removed a corner during the process (which you will likely do, you'll need to add in a new one using :CC2INSNODE: to avoid a missing portion of the poly in the corner.

To make the two polys line up exactly against the border of one of them, start by trimming the light poly to the points where it meets the dark one, then make a copy of the dark one, trim it down to just that path segment where they share a border, and use Combine Paths to merge that with the light one, this will result in them both having a border in that space.

Note that it might also be simpler to delete the lighter poly, and assuming it is drawn using a drawing tool, simply use the trace feature of the drawing tool to follow along the edge of the darker poly.

Edit: Beaten by a little mouse, but with a very different approach.

Another great looking map. Well done.

First map of the set is now in the atlas. Thanks for contributing. This is an exciting project.

I just love everything you can do with CC3+ thanks to its CAD roots. I've lost count of how many weird things I've done with it that doesn't have anything to do with mapping (Well, I guess some of them can be called mapping in a very wide definition of the term).

Multipoly combines multiple entities into one. The main advantage of multipoly is that it can be used to create holes in shapes which is needed for things like holes and some valleys.

But multipolies aren't editable, because they are a composite entity. Only way to edit it is to break the multipoly (:CC2EXPLODE:), edit the entities it is made up from ,and then reform the multipoly.