Hi Tom, so one way to do it would be to put in a dividing line down the middle of the gray curve, use Edit > Separate on the gray curve and then use Edit > Trim on the lower part of it to split it into 2 pieces:



You can then join the pieces together and there will now be a point that's directly on the grey curve which you can place on the red one, you'd grab that point and the inner 2 so that they all move together and keep the pieces smooth with each other:




re:
> Is there a way to let MOI tell me - yes the gap is less than 0,000001 now ?

Sorry no there's nothing set up in MoI to monitor curves for proximity after nudging like that.

- Michael