Page 112 - Patrick Moreau-Marine "Knots How to Tie 40 Essential Knots"

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2 - The construction of the square knot remains intact.

3 - With some materials, like leather, especially if it is new and, more particularly, if it has a square section,
add a twist using one of the two bights to increase the holding capacity.
Tied this way, it is truly like a vice.