Soft Shackles are a relatively new concept from a design standpoint. ASR was one of the first to manufacture these back in 2011, and although the design has evolved, the concept remains the same - place the knot at one end of the sling through an opening (commonly called a "noose") at the other end in order to form a loop. When placed under load, the noose tightens around the base of the knot to ensure the resulting 'closed loop' will not open. There are several types of soft shackle designs, including:
2. Modified Crown.
3. Jacketed Modified Crown.
Of all these configurations, the Modified Crown (jacketed or not) is the strongest. All ASR soft shackles are build in the Modified Crown configuration. The strength of a properly built and loaded "Modified Crown" soft shackle is approx 200% stronger than a length of rope (in the same diameter) from which it is made. Destructive testing has shown that a properly built and loaded soft shackle will break at the noose, as the knot bends over backward and pinches the loop of the noose.
Regarding how to load a soft shackle, there are varying opinions out there regarding how important it is for a soft shackle to be loaded as designed. Proper loading is depicted in the below image: