Hi PaQ, cool spaceship, looks like it is ready to slice & dice stuff up.

So for re-aligning your surface, the easiest tool for that is Transform > Orient. You'll want to place the source axis picker to be aligned to some reference points on the part you want to move, and then you'll position the second target axis picker in the same way on the target surface and that will make an alignment. So you basically need to get the axis picker snapped on to some reference points that can be repeated.

To start with, select the piece you want to move, and run Construct > Orient. Then for the base origin point, pick this point here in the corner of the surface:



So now we've got the source axis picker with the origin on the endpoint which is a repeatable target on the other surface, and the z axis direction is aligned to the surface normal there, which is another repeatable target on the other surface. But the rotation around the z axis is arbitrary, that part is not yet locked down to a known point that can be repeated on the other surface.

So the next step will be to rotate the axis picker around the z axis so that it has a known rotation around that z axis.

To do that, move your mouse over top of the x axis line:



Then hold the mouse button down and drag the x axis line while keeping the mouse down. This spins the axis around the z axis (the z axis is the primary axis having that dot on the end of it, that means that the x and y axes will spin around it when you drag them). While keeping the mouse down, drag over this endpoint here and release the button:




Now the axis is fully positioned in a way that can be repeated on the other surface.

So now you're done picking the base axis, so right-click or push the "Done" button to go to the next stage where you pick the target axis placement.

You're now going to get the target axis aligned in the same way on the other surface.

To start with go to pick the origin on the corresponding end over here:



But notice here that even though the z axis is aligned to the surface normal, it is going in the opposite direction than the first one. So you'll want to fix that - go to the option in the upper-right area of the window and toggle the option for "Flip aligned z axis":



Now go pick that origin point and the z axis will be going along the surface normal in the same direction as the first one, so now you can place it there:




Now the last step is to get the same rotation around that z axis, so this is the exact same step as previous - go to the x axis line:



Then click and hold down the mouse button and while still holding it, drag over the same endpoint as on the other part, and release:



Now the surfaces have been re-aligned, right-click or push "Done" to say you are done messing with the axis placement and end the command.


So basically to do these kinds of alignments you want to get the axis picker locked on to some particular reference points on the model that you know you can repeat on the other place.

Hope this helps!

- Michael