Cans often leave annoying rust-rings on bathroom ceramics. The culprit in my particular case was a shaving-foam canister. This clip has saved me a lot of trouble.

Check out this YouTuber's build and review of the ring! :) https://www.youtube.com/watch?v=FzyJQTmmqSw

With a ferro-based canister, rust-rings need three more ingredients to form -

1. water,
2. time, and
3. contact.
   This minimalistic clip helps by
   • adding distance between the can and the ceramic (i.e. no physical contact)
   • adding slopes and drainage, so that water doesn't stagnate under the canister
   • adding ventilation-gaps so that any water that does get under shall evaporate easily

As an added bonus, it might make your canisters 'stackable' ;)

I've used mine on a Gillette canister having base-OD of 57.6mm and cap-OD of 55.8mm. You can measure your particular canister and scale the model accordingly; the dimensions are pretty forgiving. For fine-tweaks (after printing the model), if needed, dip it in hot water (almost boiling) and let it mould to your particular canister. This method can enlarge as well as shrink the clip by a few %. On my canister, both the base and cap go on with a satisfying "click".