Dear OP to answer your question here's a common metaphor.
Think of a lock a secret and guarded hole, not meant for just anyone. Your sex is considered the fairer sex, and treated kinder and with more benefits.
And think of the man as a key, or rather having one, that fits inside your lock. And if it's a good key, then it will open that lock- giving forth good treasure.
Now, if a key can open a bunch of different locks, it's consider a master key. Usually of some importance.
However, if a lock can be opened by a bunch of different keys... well it's a shitty lock.
Make sense?
