It’s possible to do it with overlapping events, but I just thought of a cleaner method. You could maybe setup your build actor to throw out traces on a custom channel for collision boxes when placed. You could then use these hit results to remove the collision boxes of the actor you just placed. For example, if you place the build actor and then get a hit from a trace that is going upwards, you can then run an event or function that destroys/disables the top collision box component of the newly placed actor.