With a keychain, you have the starting point for all kinds of creative do-it-yourself projects.
For example, the traditional split ring can be used to attach your own knitted/crocheted animals and decorative objects to the bundle of keys or to the handbag.
The carabiner is suitable for attaching the crocheted shoulder straps you've made to bags, fixing the strap in the small ring at the bottom of the carabiner hook - this also allows you to swap the straps and play with the expression of your bag.