When I put mine on a lower two weeks ago it was my first experience with one. I screwed the locking nut on first, with the wrench-notches to the front. Then I put on the back plate with the raised-hump to the front. The hardest part was keeping the takedown-pin detent and spring sandwiched straight between the lower and the back plate. I then screwed it onto the lower until the front of the buffer tube covered the edge of the buffer retainer, but did not touch the nipple of it. Then I tightened the locking nut down. Lastly, I depressed the buffer retainer and fed the buffer and spring back into its place. I don't know how correct these instructions are, this is just how I did it.