Christy's chain was attached to loop on a collar around her neck and held by Jabba.
The chain was very long and was used to pull Christy close to Jabba when he sensed that she was distancing herself away from him. He would often tug lightly to stroke her back and make her fall against his belly, which increased his lust for her.
Jabba used the chain to prevent Christy's escape and also to control her. By tugging on the chain from time to time he reminded Christy of his mastery over her.
Christy hated her chain, as it gave Jabba complete control over her and allowed him to choke her. It allowed Jabba to have access to her body whenever he wanted, by tugging her chain to make her fall onto his belly. He would then proceed to molest her by stroking her back, rubbing her shoulders, and stroking her skin in between the cups of her bra. Along with her collar, this showed everybody that Christy was now a pet to the Great Jabba the Hutt.