Consistent with my love of analogy is my appreciation of metaphors. One metaphor I recently thought about was the metaphor of the door.Doors are "ways in" or "ways out" of (or to) something. We usually don't think about the door when we get to it - unless it is a particularly eye catching one!
However, doors are entrances (for coming) and exists (for going). They are either open (to welcome) or shut (to not wlecome). They are either locked (secure) or unlocked (insecure). They either keep out (exclude) or keep in (include).
Doors both separate and connect, demark and open - they denote passage and movement.
Similarly, doors only have meaning in relation to the people that move through them. Otherwise they are meaningless.
Moreover, there are front doors, back doors and side doors. Front doors are public & formal, for strangers, the main way in, official, you wait to be welcomed, straightforeward, aboveboard, delay, and on display. Back doors are intimate & casual, for friends, the way out, unofficial, you let yourself in, evasive, surreptitious (through the back door), immediate, and neglected. Side doors are an oblique and indirect mix of front and back doors.
From linguistics, we garner further nuances about opportunities and the door metaphor. Illustrating the idea of generating opportunities, we have the aphorisms "a foot in the door", "knock on doors", and "open up doors". In contrast, idea of closing opportunities is conveyed in the aphorisms "show someone the door", "have the door slammed in ones face", and "shut the door".