Where do we place marks after field measuring an elbow?

• A. On the outside edge of insulation
• B. Inside edge of pipe
• C. On the inner surface of pipe
• D. On the outside surface of insulation

Answer: (B)

Marking the inside edge of the pipe gives a precise reference for trimming insulation around an elbow. The bend alters direction, so the critical alignment line is tied to the pipe itself, not to the insulation pieces once they’re wrapped. By placing the marks on the pipe’s inside edge, you can accurately transfer that line to the insulation pieces and ensure the cuts meet correctly around the elbow, giving a tight fit without gaps. Marks on the insulation surface are easily damaged or obscured during wrapping, so the pipe inside edge stays as the most reliable guide throughout the installation.