Grandpa taught me that the only good wrench is one you can whack appropriately with. He made many an old girl work after a few love taps with his wrenches.

A buddy of mine told me a story about an engineering expert that helped fix some issue at NASA by hitting some equipment to make it work. Gave the line item bill to justify his expense after congress threw a fit over his price for smacking the machine . $5 wrench, $20 for travel, $350k for the knowledge of where to whack the machine or something like that. I doubt it was true, though funny still.