The word Dirk is a Scottish word for a long dagger; sometimes a cut-down sword blade mounted on a dagger hilt, rather than a knife blade. Naval and other dirks were commonly made with either double-edged or single-edged blades, and there was no standard blade configuration.

Reference books covering naval dirks invariably show the popularity of both blade types. As a consequence, historically there were about as many naval dirks mounting single-edged blades as those with double-edged blades. Some dirks have single-edged blades that also have a false edge near the tip, a feature that could be useful in a backcut.