On the v1 D7 printers the bed assembly doesn’t line up with the LCD correctly using the stop on the z bracket so this part can be added to keep the plate from being installed too far. I use to mark the top of my plate but it was still a pain when it was removed to get it installed quickly and straight. With this part I just push it all the way back and it stays aligned. This has been tested with two printers.
Print the STL then install over the existing stud on the bottom side of the Z bracket with a short M5 screw (I believe a M5x8 or 10 fits perfectly). If you have longer screws then you will need to add some washers or something. The Bed assembly should slip over the front part and the horizontal back helps keep it aligned parallel to the LCD. If you need to you can leave it a tad loose then align the plate (horizontally) before rightening.