Measure Twice, Cut Once.
Measure twice, cut once.
Measure twice because you can only cut once.
Measure a thousand times and cut once. -- Turkish Proverb
Measure twice and saw once. -- Advice from an old carpente
Advice from an old carpenter: measure twice, saw once.
Once bitten, twice shy
Measure with a micrometer. Mark with chalk. Cut with an axe.