My boyfriend once used five knives to butter a single piece of peanut butter on toast.
This was to prevent the dreaded 'contamination'. All just so I could have some peanut butter on rice cakes.
He had hugely underestimated the amount of peanut butter needed to satisfactorily cover his toast. Unable to put the same, bread-crumbed covered knife back into the jar, he got another knife, and another, until the perfect quantity of peanut butter had been applied.
Some households operate a spoon system; using a spoon in the jar and then spreading with a knife. We have a better system - we buy two jars of peanut butter.