These chrome plated his and hers key holders are a convenient and fun why to keep track of keys. Each holder has either a raised male or female icon with what looks like a lock in the crotch. A special key that fits the lock takes up residence on a key chain. The special key can then be plugged into the lock and provide hanging storage for the entire key ring.
The key holders are available on the Internet and include mounting hardware. The designs sell for about $20 - $30 each.