Page 135 - Patrick Moreau, Jean-Benoit Heron Marine Knots How to Tie 40 Essential Knots

This is a knot that sailors have been using since the dawn of time.
Using the button strap knot, you can grab any rope, moor objects, a
sheet, etc. Just before tying the bosun’s whistle knot to make a button, tie a
simple half knot in the middle of the rope.