From the factory, one of my VZ2008's had the spit locking pin installed as shown in the video, from the top with the spit end exposed under the receiver by the trigger guard. Another one of mine came installed from the bottom with the split end exposed to the inside of the receiver. I wasn't sure which was correct but after today's range session, I now know.
The split pin is under enough tension that it won't pop out no matter which way it was inserted. But it will rotate. Today I was loading with stripper clips and my magazine fell out of the receiver. I tried to put it back in but it fell right back out. I noticed that the magazine catch wasn't in the rifle. I also saw that the lateral pin that retains the bolt catch and mag release had walked out by about a half inch. The split locking pin was still tight in the receiver.
The split locking pin had rotated so that the flat part of the split was facing the retaining pin, creating a space and allowing the retaining pin to walk out. If rotated another 15 degrees or so, the split locking pin would have enough "round" to interact with the retaining pin and keep it in place. Inserting the split locking pin from the bottom, with the split end exposed to the inside of the receiver, allows the fully round top half of it to keep the retaining pin in place, no matter how much it rotates.
I was lucky that I was able to find all the springs and pieces in the gravel of the range. I would have hated to have this happen in the unlikely event of self-protection.
