Step 15: U turn
the length is in grey rods while the hight goes in blue/green rods. This is propably not a good combination if sizes are based on blue rods (horizontal/vertically). However, This should work on red rods aswell. Make sure the ball can get enough speed to overcome the resistance the yellow connectors give. Or build it solely out of the yellow (or orange) connectors.
The last image shows how one U turn goes and has the flexible rods for the next turn connected at one end. The process just repeats itself in both directions.
This u turn is used to create a zig-zagging path. But it can be used as a single element aswell.