A reef knot (or square knot) cannot be adjusted or tied under load. When you tie the second crossing, the first one always loosens a bit. The lapp knot in the

A reef knot (or square knot) cannot be adjusted or tied under load. When you tie the second crossing, the first one always loosens a bit. The lapp knot in the video can be tensioned properly after tying, which is pretty slick.