Hello,
I don’t know how to normalize the extrusion to always be upwards instead of going down.
It goes down when the leaves count is odd and upwards (how I want) when its an even number in the number slider.
Hi @Leo13, can you clarify what your problem is? The only object that looks ‘upside down’ is getting extruded with a negative number:
If you put the linear array number slider in any even number, this rectangle box wont be going down. Or if you just disconnect the negative component of the box rectangle it will go only upwards if the number of leaves (linear array number slider) is an odd number.
Quick hotfix:
Box rectangle height always positive doubt.gh (26.7 KB)
It works, but you know to explain to me why flip surface doesn’t work in this case and need to transform it in mesh to do this?
Hi, you don’t have to transform it to mesh - but in this case it just made it easy to do so (because it’s a simple rectangle) to quickly grab a handy Flip Mesh component to do the same (but with less steps) as getting the surface plane and reversing the normal. First, because there’s no Flip component for surfaces (but maybe I am wrong and you can use Flip Crv or Reverse Surface components I skipped); and second, since you’re relying on box extrusion, it goes off the plane of the rectangle you’re extruding as box. Other than that, I am not qualified to answer ‘why’ an odd number of objects makes the surface ‘negative’ vs ‘positive’ to then cause the box height to point up or down, but I think this is both predictable and expected for reasons I definitely can’t explain 
Someone from Rhino dev team could explain this? I am really curious @bobmcneel @DavidRutten
Nevermind on that, I didn’t get consistent results when guaranteeing surface/curve is flipped prior to rectangle-box extrusion, so even less qualified than before to answer anything about that!
When the rectangle/surface plane normal points up, rectangle extrusion goes down (WHY? Who knows :D), but Flip Crv does work; hence one way to chaperone the behavior before the extrusion (and skip meshing) could be like this:
Box rectangle height always positive doubt (2).gh (31.1 KB)
nice! but the mesh solution was simpler and already enough, but good to know this one aswel. But, the whole situation still boggling my mind.
Don’t seek answers—you’ll just end up with more questions haha
Jokes aside I did forget there is a native Flip Surface component but even though it does flip the surface normals it doesn’t tweak the XYs like Flip Curve did—furthermore, Box Rectangle doesn’t care and still just takes in a rectangle each time, but without proper axis adjustment (not just the surface normal) the width and length of the rectangle can get swapped. I know I’m not answering why it happens, just describing what happens 
Cheers!
Hahaha, by questioning we understand the world better, but maybe this won’t be good, right?
Yes, I tried the surface flip before, but it seemed useless. The mesh flip is way better.