I recently made my first attempt at a diamond braid. I used black and tan 550 paracord and made a choker of sorts. I used a lanyard knot doubled up to start. To keep the knot from collapsing on itself i put a single strand of black 550 paracord through the loop, finishing it off with another lanyard knot. I then used the diamond braid to get it roughly the length I wanted. To end it I used a snake knot to whip the end. Leaving a loop to capture the lanyard knot in.
