Adding a Block Into Region Using several different themes, I'm looking to add a generic region to the bottom of each "content" section of my webpage. The code I have so far is. . . . with Social Share being the name of the block.
If you have all of these different themes enabled (and you aren't using something like Panels), then you can simple edit this from the Block administration page (admin/structure/block).

If you want this to be completely removed from configurability, then I would recommend either doing a preprocess function for the content region (or hard-coding, ick, your custom HTML into the region itself).