Transom

1. A lateral member fastened inside the sternpost, to which the hull and deckplanks are fitted.
2. The aft "wall" of the stern; often the part to which an outboard unit or the drive portion of a sterndrive is attached.
3. A more or less flat surface across the stern of a vessel. Dinghies tend to have almost vertical transoms, whereas yachts' transoms may be raked forward or aft.