color("red")  // this is your old part. notice you have to flip it

    rotate([i,0,0]) 
    translate([0, 0, 10]) 
    cylinder(h=90, r=0.5); 
} 

You can see why you had to rotate it negatively in the code below (I exaggerated the rotations to make it easier to see). Also, by exaggerating the values, an imperfectness with the geometry becomes apparent. The planes sort of overlap. I'm no expert, but I think it's not going to matter in practice, because the thickness of the planes covers up the gap (with the proper rotation values). module quarterPlane() { color("Blue") rotate([22.5, 22.5, 0]) translate([-23.49,0,0]) // create the part in the other quadrant and you need to rotate positively to get up towards 30 degrees. cube([23.49,19,.02]); color("red") // this is your old part. notice you have to flip it negatively to rotate the outer edge from 180 towards 150, because 150 is less than 180 rotate([22.5, -22.5, 0]) cube([23.49,19,.02]); } quarterPlane(); module protractor(c) { color(c) for (i=[0:30:359]) { rotate([i, 0, 0]) translate([0, 100, 0]) rotate([0,90,0]) linear_extrude(height=1) text(str(i)); rotate([i,0,0]) translate([0, 0, 10]) cylinder(h=90, r=0.5); } } rotate([0,0,90]) protractor("chartreuse"); -- View this message in context: http://forum.openscad.org/geometrically-confused-tp10421p10429.html Sent from the OpenSCAD mailing list archive at Nabble.com.