J-signs allow you to attach the sign without reattaching the rope. Bending back the "ear" of the sign allows you to feed a rope or chain through the sign. J-signs are often used in conjunction with that can easily be changed, according to the recent radiological conditions.
 

U.S. Patent 5092066 Ears bend to accomodate arope.

J-sign hanging from a chain.

J-sign hanging from a rope.

Change inserts easily.

Also see:
    J-sign Specification