First off - this is the final look of the desk:
The problem is that the white rails for the keyboard tray - I don't know where to attach them to the desk. I have three 727x510 milimeter planks that the top plank(the 1100x590 one) should be attached to. However I'm not sure which way should be up or down. Te 350 milimeter rail should be attached like you see on the picture, but I can't find the proper spots. Maybe I have them the wrong way? All three planks have four holes at the top which match the three lines of holes on the top plank, so I assumed that's where they attach to it and that's their top part. Their other part is smooth. Here is what I mean:
On the other hand, i have these "legs" that look like they match the holes in the "top part":
Here are pictures of the three planks front and back.
The order of the planks is the same on both the front and back pics. Here is the top plank's bottom side:
Can anyone give me a clue on which direction they should all be facing and where to put the tray rail? It doesn't match any 2 holes and if I screw it to a single hole it'll just rotate around it...that's not right.