The Anchor Bend Knot isn't a bend or a knot; it's a hitch. Sailors of old referred to 'bending-on an anchor' and the name of this knot originated from those times.
It's an extremely strong and reliable knot, much more so than the commonly used bowline or round turn and two half-hitches. Consequently, the anchor bend knot should be your first choice when making a long-term attachment to a shackle or similar item of hardware.
But why 'long-term'? Because once it's been under tension the anchor hitch can be almost impossible to undo.
Take a turn through the shackle.
Then take another one. After all one good turn deserves another!
Now pass the working end through both turns. If you cinch the knot up tight at this stage you should sieze the the working end to the standing part.
But for a super-strong and reliable connection with no need for siezing, pass the the working end through both turns a second time.