Need Help! Locking Nut orientation

Hello, I bought a SFU1605 ball screw set from Amazon. It came with a BK Support, BF Support, Nut Housing, Locking Spring, Locking nut and Coupler. The Locking Nut has one side showing the silver metallic screw thread. Is that side supposed to be facing (touching) the BK Support or the Coupler? The seller said it should be facing the Coupler but on youtube, I have seen two persons doing it the opposite way. Could you please let me know which is the correct orientation and why?

This is a companion discussion topic for the original entry at