Hold, witness and review points in third-party inspection

An Inspection and Test Plan (ITP) converts project quality requirements into a sequence of manufacturing, testing, inspection and documentation activities. The familiar letters H, W and R define how the purchaser, third-party inspector or other nominated party participates at each stage.

The exact definitions and notification rules are contractual. The approved project ITP always takes precedence over informal industry shorthand.

Hold point — H

A Hold point is the most restrictive intervention point. Work is not supposed to proceed beyond that stage until the nominated inspecting/approving party has attended or formally released the hold in accordance with the contract.

Typical examples can include:

• approval of a manufacturing procedure before production;
• witnessing a critical qualification test;
• release before a destructive test consumes the only representative sample;
• final release before shipment where the ITP requires it.

A supplier should not assume that sending a notice automatically converts a hold point into permission to continue. The approved ITP must define the release mechanism.

Witness point — W

At a Witness point, the nominated party is invited to attend and observe the activity. In many ITP systems, if adequate notice has been given and the inspector elects not to attend, the supplier may proceed — but only if the contractual definition allows this.

Common witness activities include:

• mechanical testing;
• NDT demonstrations;
• dimensional inspection;
• hydrostatic testing;
• final inspection.

The distinction from a hold point is practical: a witness point normally gives the inspector the right to attend, whereas a hold point normally prevents progress until release.

Review point — R

A Review point is primarily a documentary intervention. The inspector or purchaser reviews records rather than necessarily attending the physical activity.

Examples include review of:

• MTCs;
• NDT reports;
• calibration certificates;
• WPS/PQR or manufacturing procedures;
• dimensional reports;
• traceability records;
• final manufacturing data books.

A review point can still be contractually important. If documents are incomplete or non-compliant, release can be withheld even though the original activity has already taken place.

Surveillance / monitoring points

Some ITPs also use S for surveillance, monitoring or spot inspection. The nominated inspector may visit or observe on a sampling basis without the supplier being required to stop at every occurrence.

Because abbreviations vary between clients, never infer a legal/contractual meaning from the letter alone.

Who is the “third party”?

A third-party inspection body is expected to operate competently and impartially. ISO/IEC 17020:2026 is the principal conformity-assessment standard for bodies performing inspection.

But a project may nominate:

• the purchaser's inspector;
• an independent TPI agency;
• a classification society;
• a notified/recognized body where regulation requires one;
• an end-user representative.

The ITP should identify which party owns each H/W/R point, not merely put an “H” in a column.

H/W/R is not the same as EN 10204 certificate type

A project may require a 3.1 MTC and still have TPI witness points. It may also require 3.2 certification with a specific independent validation route.

The inspection-document type and the ITP intervention plan are related but separate. See EN 10204 3.1 vs 3.2.

What a good ITP should state

For each activity, the ITP should make clear:

The notice period is especially important. A witness point is of little value if the inspector receives the invitation after the test has already taken place.

Procurement takeaway

Do not write “TPI required” and leave the intervention undefined. Agree the ITP before production, identify the responsible parties, define H/W/R terminology and notification periods, and make sure any point needed for 3.2 certification or regulatory witnessing occurs before the activity becomes impossible to repeat.

References and verification sources

• ISO/IEC 17020:2026 — Requirements for bodies performing inspection
• BHEL public tender documentation — example H/W/R definitions