Nite Ize G series Carabiner hooks on to my pants and holds the smaller Nite Ize micro lock with keys.

https://niteize.com/g-series-dual-chamber-carabiner

Nite Ize micro lock stainless steel holds key sets (House and car, work and storage) that connect to the larger above carabiner.

https://niteize.com/s-biner-microlock-stainless-steel