The marlinespike is a shipboard tool that looks like an ice pick or large needle. Depending on the type of marlinspike, it has a round wooden handle a round blade with a sharp point. It was used to separate strands in marlines. Marlines are two lines of tarred rope that are loosely wrapped together in a left hand turn. Over time marlin spikes became smaller. today many pocket knives have a blade that is called a marlinspike.
In times of crew dissatifaction (mutinies) the marlinespikes were a readily adaptable tool used as a weapon. Most captains locked weapons away unless a battle was pending for fear of armed mutinies. However such things as marlinespikes and balaying pins had to remain available to the crew in order for the ship to function. For this reason the marlinespike became the favored weapon of mutineers.