Saving while against iron bar teleports you vertically when logging back in.

If you save when you are right up against an iron bar, once you log back in, you will appear in the closest open space above that location. If used as shown in the attached screenshot, this can be used with a single block column to teleport to the top (up to build limit).

I could only get this to work in the overworld, i.e. I couldn't get to the top of the nether with it.