Page 88 - Patrick Moreau - Marine Knots How to Tie 40 Essential Knots

If you need to create a non-sliding eye with a very slippery material like pure
Dyneema, the bowline knot may slide. So in this case a special knot is used: the
Matthew Walker knot. While it is generally tied with several strands, it can also
be done with one eye, with the equivalent of a second strand, which is tied in the
first half knot.
Originally, this knot was used to start the crease in the deadeyes, which, with
their three holes, allowed the shrouds to be stretched and straightened.

1, 2, and 3 - The two half knots are now intertwined.