1. Begin assembly

FYI for anyone doing these steps to upgrade from the original design, this requires hardware that doesn't come with the original printer. See step 14 and step 20. You need two additional m3 square nuts and 2 m3x10 screws for the new design. @Prusa, you should probably mention this somewhere up here near step 1...

You only need to print one of the jigs.

There has been posted problems on Prints stopping mid-print and the know issue identified is that the cable connector comes loose. 
so this is a quality of life update and Prusa did not bother to notify previous owners of the XL about this.  We had to search and research on our own that lead me here. Prusa being is notable of making things right. You should have informed us of this and sent us the needed parts. 

It appears that this new part has not been listed in the eShop yet. It is, however listed in printables.com under the XL printable parts (https://www.printables.com/model/449554-xl-printable-parts/files).