up against the wood

On the edge of your ability or capacity. Literal definition comes from being right up against a wood railing or wall with no where to go. Typically refers to being pressured, busy or at your limit.

This project has me up against the wood this week.

Diamonds up against that wood

The word perfectly describes wearing diamond rings on your hand, while grabbing a "wood" grain steering wheel.
This term is mostly used in the Southern region of the USA, more specifically in Texas, and was popularized by the legendary Texas duo, UGK (Pimp C and Bun B) on their song, "Diamonds & Wood."

Mayne, you can't mess with my Slab, when I'm ridin' around, with my Diamonds up against that wood.