A hammer’s head. A knit of threads. A scoop on top. Food after bed.

In the navy, ships are for floating, while these are likely to sink. They aren't submarines, though they fall under this four letter word. Though to the rest of us, these and ships are both quite the same.

This tool helps fix up teeth, Or create tunnels for mining, Though exercises named by this May need some refining

In stories and skeletons I’m easy to find, yet some cowardly folk are told to grow one of mine.

You've got diamonds in your eyes, Or a bird of prey in your sight. Children chase after me as I take flight.