Answer
Line segment $\overline{EF}$
Work Step by Step
Use your compass to measure segments AB and CD. Align them to subtract the length of segment CD from segment AB. Mark the end points of the new segment as E and F.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.