Threshold

The OED states the definition of threshold as:
"The piece of timber or stone which lies below the bottom of a door, and has to be crossed in entering a house; the sill of a doorway; hence, the entrance to a house or building."
or
"In reference to entrance, the beginning of a state or action, outset, opening. (In quot. 1659, in reference to going out or leaving, close, end.)"

The etymology doesn't seem very interesting. Apparently it comes from the Old English word "therscold."
There are two interesting aspects of this word for me. The first is that the word threshold is usually associated with entering. Most of the definitions in OED (there were others) associated the threshold with the act of "entering." It seems that, most of the time in modern English, it is associated with the act of entering. So it was interesting to see that the last time the OED had a quotation where "threshold" was associated with exiting was in 1695.

The second reason for my interest in the word is in the imagery that the word presents me with. So as I ask you: What do you imagine when you hear the word? Is the room you're in dark and the place you're going into light? Is it the opposite case? Do you even picture a door, or do you just see the plank of wood/metal strip/etc. that is the threshold? Does the imagery that comes to mind mean anything?