Hi. I noticed the newer versions of Arduino Nano have what they call "tessellated connectors".
I can see that you could solder the regular header pins in the normal way. Are you supposed to also be able to solder them in a sideways/horizontal orientation?
Other than header pins, are they made for some other connector to go there?
Thanks for your help.
They are mainly for placement on another PCB. Take a look at some GPS or Wifi modules and you'll see the same thing.
[tt]castellated[/tt]
Thanks! That was so much easier to find information on, once I knew the right name. 
I found this video on YouTube that gave a nice demonstration of how it would be used.
And it does look like a nice way to put one board onto another one.
As long as there are components only on the top side of the daughterboard.
Otherwise (and it is an option) you have to cut out part of the motherboard! 