Bladew scores - Pic heavy with a few extra thrown in...

[Cutshaw]

That is a frog fitting. You can use it with a carrier or just tuck it in your waistband to hold the sheath in place. It doesn't have a retention function. That blade looks like it is held in by gravity and friction alone.

rb is correct. Sorry, I missed that question. It fits by friction alone. Solid but slides in and out softly. The double cut finish just glides in. It has also open up the sheath enough that the HHFSH works well too.