Sam: Right thumb

The thumb is known for wealth, particularly for men, as it was historically a symbol for showing off expensive rings (as the larger size made them more costly) on their thumbs. It can also be seen as a sign of courage and strength, as archers commonly wore them to protect their thumbs.

Kojima mentioned that Sam wears his on his thumbs for the likes but I also see how strength and courage play into his character. He is THE delivery man, the man who has gone through so much grief and yet he pulls through for others and doesn't give in to selfish thoughts. He is strong and courageous for the work he does but that doesn't stop him from being vulnerable.

Fragile: Right thumb (specifically on her gloves)

As mentioned with Sam, I think this goes for Fragile in a similar way. She has been through a lot, and pushed through with her determination and strength. She's fragile but not that fragile. However, I think that her ring being placed on the gloves is interesting because I think it ties into her detachment from the crew. After what happened with Higgs, although she is there with the crew, as we later find out, her ha was biding time before it finally caught up with her. Her ring not really being attached to her own hand symbolizes this to me.

Rainy: Right pinky finger

The ring on the right pinky is known for having reached professional achievements or personal accomplishments. it can also be known for wearing it on that side for style and showing off a persons individuality.

I believe this is important for Rainy as she had been previously ridiculed for her DOOMs ability with the timefall, and she was on the verge of killing herself before Fragile found her and helped her realize she wasn't just destructive as she also had the ability to create corefall. Rainy shows off her individuality from others, now not as a weakness but as a strength as she now uses her ability to help others like Sam.

Tomorrow: Right pinky finger

Again, I think the individuality aspect is still important here. The fact that Rainy is the one to place the ring of Tomorrows pinky, just like her, shows how similar the two are. Both have aging related abilities, both started out unable to control it. And just as Rainy learned and joined people who cared about her, so did Tomorrow. Tomorrow reaches a lot of accomplishments, but the biggest being regaining her memories as Lou and rebelling against what Higgs was trying to use her for.

Tarman: Left middle finger

Wearing a ring on your middle finger is seen as bold, as it is the more unusual places for a ring. Having a ring on this finger can be a sign that the person is looking for solace and stability in their life, and the ring is a helpful reminder of that.

I believe Tarman still feels a bit guilty over the loss of his son, and he even mentions his hope that his son might still be there to watch him, ties into the part about looking for stability. His hope that his son's ka might be out there is keeping him from spiraling into feeling too guilty about what happened.

Heartman: left ring finger

The ring finger is most commonly known for marriage. it symbolizes love, creativity and most of all, commitment to another person. In ancient civilizations, it was believed that the ring finger has the 'Vena Amoris', Latin for "vein of love", which connected directly from that finger to the persons heart.

This one I feel is the most obvious. Not only is Heartman still looking for his wife and the devotion is to his wife, but also his devotion to finding her and their child on the beach.

Die-hardman: left index finger

A ring on the index can be symbolism for self ambition, authority, and dominance. the index is the dominant finger, so that dominance translates into the ring position. Historically, a lot of important family's had their rings on their index to flaunt their status and leadership.

This one is my favorite because it shows Die-hardman's growth from DS1. It's kinda like he's taken the mantle from the two people he loved (Bridget and Cliff) and now he is the one in charge of his life, and of others. Die-hardman is the leader behind Drawbridge's operations and instead of hiding behind a mask, he is taking charge and pushing back against those like APAS who seek to destroy humanity like Amelie did.