Key
You take some gold and cover your yoga brush in it, turning it into a key. You shove the brush you normally use for yoga into the lock to your car and pour the gold over it. Now it's the right shape to be a key!
You lost your old key, you see. But you're a go with the flow type of person, thanks to all the yoga, so you make a new one!
けん
かぎ
None
This key has to be perfect, because if it isn't the car guillotine (かぎ) will come down and chop off your hand!
Imagine carefully putting your makeshift key into your car's lock. You close your eyes and pray that the car guillotine isn't going to trigger, knowing it isn't a legit key.