Related:

• Uncle Ed's Rule of Thumb: Never use your thumb for a rule.
  You'll either hit it with a hammer or get a splinter in it....
• Uncle Ed's Rule of Thumb: Never use your thumb for a rule.
  You'll either hit it with a hammmer or get a splinter in it....
• When hammering a nail, you will never hit your finger if you hold the hammer with both hands.
  -- Leibowitz's Rule...
• Leibowitz's Rule: When hammering a nail, you will never hit your finger if you hold the hammer with both hands.