Example of a typical <a href="https://en.wikipedia.org/wiki/gun_port" class="extiw" title="en:gun port">gun port</a> of a 36-pounder battery on a 19th century ship.
<a href="//commons.wikimedia.org/wiki/User:Rama" title="User:Rama">Rama</a>
CC BY-SA 2.0 fr
<span class="int-own-work" lang="en">Own work</span>