Strictly speaking, it is probably not accurate to talk of two dimensional models in mtm2.  But, for the sake of learning BinEdit, let's assume a 2D model is anything that has only one side visible.  Naturally, then, a simple 2D model must be either a triangular or four-cornered bin.  Examples of 2D models would be all the trees in mtm2, the cover to the secret passage in Chase the Dragon by Guitar Bill, and the "wrong way" signs in Dark Star by Oliver Pieper and in CNR 008 by GyverX.  There are more, but that should give you the idea.  The point here is that these models, like a sheet of paper, all have a width and a height but no thickness/depth of any significance.

Quick Review

To make a bin we need to do three things

1. define some verticies
2. tell the face which verticies to use
3. apply a graphic texture to the face