Gunnel here is the same thing as a gunwale: the top edge of a boat’s side — the rail you rest your hand on, sit on in a small dinghy, or hook an oar over. Sailors say both; gunnel is how the word often sounds, and how it is often written in casual boat talk. On old warships that edge was a thick timber that helped hold the ship’s guns, which is why gun and wale (a raised plank or ridge) sit inside the word — though today most boats with a gunnel have no guns at all. It is boat English, not everyday city English. Though actually, a gunnel is also a small eel-shaped fish; that is a different word with the same spelling. This entry is the boat edge.

舷緣、船舷上緣（gunwale 的口語拼法）