Merlon

A merlon is the solid, upright section of a battlement in medieval architecture or fortifications. Merlons are sometimes pierced by narrow, vertical embrasures, or tooth-like slits designed for observation and fire. The space between two merlons is called a crenel, and a succession of merlons and crenels is a crenellation. Crenels designed in later eras for use by cannons were also called embrasures.

Nothing on the board — the decks are resting.