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I have a "hiker's clip" attached to my purse handles. When I get home and inside, I immediately attach my car and house keyring onto the hiker's clip.
I keep my car keys beside my bed on my beside table for two reasons.
When packing holiday leftovers to send home with guests, put their car keys in the fridge with the leftovers. They will think you are nuts, but they won't get any farther than the car door without their keys - and the leftovers!
My husband is constantly losing his keys. He is always spending about fifteen minutes of his day looking for them. My friend told me to use a shower hook or carabiner. Attach the keys on the hook and put on the zipper of your backpack. If you don't want them seen, tuck inside backpack still attached to your zipper.
I hook my keys to an item if I need to remember to take it with me or bring it home from work, even if it is in the refrigerator.
I have a 6-hook over-the-door-hanger on the closet door next to my front door. As soon as I come into the house, I hang my keys and purse on one of the hooks.