Had this thought while turning beads last night, I’ve seen others do this, and I used to do a few when my beads included modified cartridge cases. Bored one end of a pair of my medium sized aluminum beads out larger. Forms a snug fit over a knot tied in a single strand of u-gutted 550 cord.
(Yes I know I need to re-trim the flash on those holes… I somehow missed it before polishing them.)
I need to play with the hole size. See if I can get one big enough in this metal stock, to fit over a knot of two strands of gutted 550. So that they could be put on loops of 550 cord.
I know I can fit that into my magnum beads, but I’m not sure it can fit in this “large” size and leave material for much of an outer design.
Also need to try it in my “small” sized beads, a hole size combo that will fit micro cord knots.
Alaskan, Adventurer, Engineer. 
That is a great idea! Housing the knot inside the bead makes it look really sharp!