A hand-saw is a good thing, but not to shave with.

Something may be useful and well made while still being wholly unsuitable for a particular task. Merit in one setting does not make a tool, method, or person appropriate in every setting.

Figuratively, the saying cautions against crude misapplication: choosing an available or powerful instrument rather than one that fits the job. It favors judgment, proportion, and means unlikely to damage what one intends to handle.

Use it figuratively when a proposed solution has genuine value but is excessively harsh, awkward, or ill suited to the immediate problem. It can gently criticize one-size-fits-all thinking in practical decisions, management, argument, or problem solving.