PURPOSE: To prevent a proofmark form for use in reinforcement joint sampling inspection from being peeled after use from a sample unless some destructive means is taken, such as cutting it apart.

CONSTITUTION: A proofmark form main body 11 has an opening 13 formed in almost the center of a form 12 and sized to allow the entire joint part of a sampled reinforcement joint to fit into it. Lists 18, 18B with the required items 19A, 19B and blanks 20A, 20B are displayed on the appropriate portions of the surface of the form 12. The proofmark form main body 11 is securely wound on the sample with the joint part exposed through the opening 13, and is attached to the sample with the upper and lower ends of the form 12 affixed together.