what is the name of the drop out screw tensioner thing??
 

and what is the proper alignment/adjustment of this thing? It seems pointless as my rear derailleur takes up the slack of the chain anyway. However, I could be missing something and maybe it does serve a purpose??

Here is a pic of one. *pic stolen from soradicals flickr cuz i think his bike is hot*
http://farm4.static.flickr.com/3364/...182e8ccc04.jpg

They're called "dropout screws".

Their function is to speed wheel changes by providing a solid stop for the axle on both sides. That way (once they're set) you don't have to visually align the front of the tire with the frame.

It's called a dropout adjuster. It merely helps to locate the rear wheel squarely. It seems like there is always an active thread asking about them.

cool thanks. Hmm.. i guess frames were not as straight as they are now seeing as my two newer bikes have vertical drops with no room to shift it up-down (or side-to-side in this case)??

Niagara has them:

http://www.niagaracycle.com/product_...ucts_id=407258

I bought a set to replace a bent one on my PUCH.

They also help with Single speed set ups and chain tension.

The frames were straight, but with horizontal dropouts one can adjust the wheelbase of the bike for different rides.