This is a simple model my son asked for. It allows the ball to freely drop until it reaches “Catch” part. The attached profile will allow you to have 3 drops until it reaches the catch but you can easily clone/remove any of the parts to make it longer/shorter. For each part I'm attaching two versions - one with and second one without the stop. The stop is there to prevent the ball from going through the block when dropping down. The very top part should have no stop as the marble will need to roll into it. By contrast each part that is ‘catching’ the ball should be printed with the stop.