Safety Thimble: Uses Less Connection Points with a Bow Shackle. One of the most impressive features of the Safety Thimble is the shape of the “eyelet” in the thimble. This purposely designed eyelet was originally designed for use with 3/4″ Bow Shackles (usually misnamed as D-Rings, but can also be referred as an Anchor Shackle). The eyelet on the Safety Thimble uniquely allows a 3/4″ Bow Shackle to be inserted into the Safety Thimble using either the “pin” end or the the “loop” end. Why is this significant? Because this allows the use of only one Bow Shackle to be used in a recovery. Winch Thimbles designed with just a round eyelet requires the user to use 2 Bow Shackles to make a connection. As everyone is aware, using less connection points reduces the amount of breaking points during winching. Less breaking points means less chance of a catastrophe happening while you are winching under a load.