Hi Rudl, well you can create a dividing plane like Burr is showing above and then do a boolean difference on each frame using that same dividing plane as the cutting object. That will slice each frame to a common plane.

But since the objects are not aligned to one another they will not naturally touch each other when cut at a single common plane, your objects just do not naturally align with one another.

If 2 objects made up of planes touch at one corner but are at totally different orientations to one another, they just do not geometrically touch each other when both are cut by a single plane...

Maybe you want something more like the different planes being extended beyond the current boundries of your frames until the extensions intersect one another. You'll probably need to do something like that by making larger planes by scaling them up and then using Construct > Curve > Isect to intersect planes with one another to get your boundaries.

- Michael