Think of a master link, the type with the removable clip used on final drive chains. You know what I'm talking about, two pins welded to a side plate, push the pins thru the ends of the chain, add another side plate, hold it all together with a spring clip. Easy Peasy.
Now, imagine if you instead assembled it this way... Side plate with pins followed by the second side plate, push the pins thru the chain ends, hold it all together with the clip.
That's right, he/she has BOTH of the side plates one ONE side! That poor little spring clip doing its best to hold the other side by itself! The extra thick side gauging the case while your at it too!