The mini-bend is a very useful and versatile piece, and something you want quite a few of as they can be utilised in lots of ways. They can be used as a ramp, in series, to change direction (very useful for burning off excess marble speed), and is a must have accompaniment to the spinner.
Laser cut plywood
Magets, and laser cut silicon non-slip stickers (so it grips the vertical surface)
Instructional build video.
Build time: 5 mins
Paint brush and wood glue not included, but if you need them check my shop.