I took the plastic off of the W916 wing tip ribs and did not mark them left and right before doing so. I tried to determine which piece of plastic was on top in the garbage can to no avail! If anyone knows how to tell the two apart it would be greatly appreciated.
My RV-8 manual says in the section "preparing the ribs":
Ribs may be either "left" (suffix L, i.e: W-709-L) or right (suffix R, i.e. W-709-R). You may identify the "hand" of a rib by holding it with the leading edge away from you with the flange closest to the tooling holes towards the floor. If the flange is on your left, the rib is an "-L", if it is on the right, it is an "-R".
That's true, the "-L" and "-R" only specifies on which side of the web the flange is. The plans then tell you where you have to mount what kind of rib. This makes perfect sense. The part number (including the L/R suffix) only specifies the part itself, in this case a rib. The rib on its own doesn't know where it belongs. In fact you need the -L kind on both the left and the right wing (same for -R), and if you used the suffix to specify the final location of the rib rather than its shape, you would end up with identical parts having different names. As it is now, there is a very clear mapping between name and shape.