Fast key identification with nail polish
I have two keys on the keychain which are from the same company of a lock manufacturer. One is logically for our front door, the other belongs to the front door of my parents' house. And every time I'm guaranteed to catch the wrong one when I catch up.
It is not these classic round keys, for which there are such colorful rings, but square keys. In addition, I find these colored rings not so great, often these are gone out with round keys already. Of course there is the possibility to make a key in a certain color at the key maker, but that does not work with locking keys, which are available, because there you can not do nothing to imitate me.
Since I have all my keys on a bunch and this has to stay that way, I just made a dab of nail polish on one of the keys, so I always know which one to grab at my door.
Made fast, even without plastic ring. If you have several similar keys, for example, the work, office door, etc., you can of course make several markings with different paint colors (home = red, office door = orange) which paints the drawer of the wife or their own has to offer.
Edding has not proven itself, rubs off after the time in your pocket / purse again, or fades. Paint keeps much longer.