An interesting old trick taught in undergraduate chemistry was called the titration thief. Now a titration is something one does to measure the titer of an unknown solution. It's usually an acid-base or some other strength-of-this vs. strength-of-that determination.
The gist of a titration is that one slowly drips a solution of a known strength into a solution of an unknown strength (but of opposite polarity) until some indicator indicates neutrality. The exact point of neutrality is called the endpoint. It used to take me quite a bit of practice to reach but not exceed that delicate endpoint without overshooting.
A titration thief was a trick whereby one removed a tiny bit of the unknown solution beforehand in case the endpoint was overshot. In the event of an overshoot, the small amount of unknown was added back in and the endpoint was then re-titrated with greater care.