How do I remove vertical space between postbits in showthread.php (3.6.7)?

[NutriaMagnate]

If you'll notice, there's a small gap of background color between each post and the one below or above it. This is a style feature that most custom skins don't seem inclined to mess with, but my users are interested in having this gap removed -- the thread should look like one continuous table with no gaps.

I've looked around in the showthread and postbit templates and I'm stumped. Anybody know how to do this?

*edit* Resolved. The bottom margin of the postbit tables is found in the template, "postbit_wrapper."