To follow Lewis Carroll’s Preface in The Hunting of the Snark (internal link) you must know what a bowsprit and a rudder are. The latter’s form and function is common knowledge, the bowsprit less so.
According to the good folks at WiseGeek.com (external link), the bowsprit is
A bowsprit is a long spar or pole that extends from the front of a sailing vessel. It is usually made of wood but can be made from other materials as well. The bowsprit acts as a securing point for ropes attached to the sails, allowing the ship to position the sails further forward on the ship. This pole extends off the part of the ship known as the prow, which is the point of the ship farthest forward in the water that cuts through the water, allowing the ship to move forward at higher speeds.
Thus, Carroll mentions parts fore and aft, completely opposite from each other.
Here, now is an excerpt from his Preface:
If—and the thing is wildly possible—the charge of writing nonsense were ever brought against the author of this brief but instructive poem, it would be based, I feel convinced, on the line (in p.4)
“Then the bowsprit got mixed with the rudder sometimes.”
In view of this painful possibility, I will not (as I might) appeal indignantly to my other writings as a proof that I am incapable of such a deed: I will not (as I might) point to the strong moral purpose of this poem itself, to the arithmetical principles so cautiously inculcated in it, or to its noble teachings in Natural History—I will take the more prosaic course of simply explaining how it happened.
The Bellman, who was almost morbidly sensitive about appearances, used to have the bowsprit unshipped once or twice a week to be revarnished, and it more than once happened, when the time came for replacing it, that no one on board could remember which end of the ship it belonged to. They knew it was not of the slightest use to appeal to the Bellman about it— he would only refer to his Naval Code, and read out in pathetic tones Admiralty Instructions which none of them had ever been able to understand— so it generally ended in its being fastened on, anyhow, across the rudder. The helmsman1 used to stand by with tears in his eyes; he knew it was all wrong, but alas! Rule 42 of the Code, “No one shall speak to the Man at the Helm,” had been completed by the Bellman himself with the words “and the Man at the Helm shall speak to no one.“ So remonstrance was impossible, and no steering could be done till the next varnishing day. During these bewildering intervals the ship usually sailed backwards.
More on the Hunting of the Snark here: http://blog.snrk.de/
The bowsprit partially in view, above the figurehead.