One of the many documents sent and received by Josiah Fox regarding the construction of frigates in 1796 discussed a rumor that the night heads had not been raised with the frames. From the context, a night head must be part of a ship, but what is it?
The term appears in a 1781 book Naval Architecture, or the Rudiments and Rules of Ship-Building spelled as “knighthead” not “nighthead”. It is used as a reference point when taking measurements, often referred to in conjunction with hawse-pieces. A hawse is the part of the bow, or forward part, of a ship in which holes (called hawse-holes) are cut for cables to pass through. Knightheads are therefore part of the bow. According to the Oxford English Dictionary, they are a large timber which rise from the keel to support the bowsprit, the large spar which extends forward from the bow. The knighthead is an important part of the strucutural integrity of the ship.
With this information, it makes sense that Fox wanted to reassure his colleague that the knightheads had, in fact, been raised with the frame of the frigate.