Third-party inspection that actually catches defects.

A hold point is a step in the fabrication or execution sequence where work cannot proceed without inspector sign-off. Witness points are notified but do not stop work. Third-party inspection value comes almost entirely from the hold points — the inspector's presence at the right stage, with the right acceptance criterion, and the authority to stop the line.

Weak inspection programmes have too many witness points and too few hold points, which leaves the inspector present but powerless.

'Weld to be visually acceptable' is not a criterion — it is an opinion. 'Weld to be visually inspected to AWS D1.1 §6.9, with no cracks, no undercut greater than 1mm, and complete fusion at the toe' is a criterion. Every hold point in the ITP must reference a specific code clause, spec section or drawing note that both parties agreed to before fabrication began. This prevents the recurring dispute: 'you signed it off last month, now you are rejecting the same defect'.

Catching a defect at the machining stage costs one unit. Catching the same defect after coating costs ten. Catching it after installation costs a hundred. Third-party surveillance placed at source — the fabricator's shop, the foundry, the pipe mill — routinely catches 3–5x more defects per inspector-day than the same programme placed at receiving inspection. The additional travel cost is repaid many times over in avoided rework and schedule protection.

An inspector without documented stop-work authority is an observer. The inspection agreement must state, in writing, the conditions under which the TPI may halt production, the escalation path, and the client contact who ratifies the hold. Without this, the inspector will be pressured to sign 'under observation' notes on defective work — and every one of those notes ends up as a Major NCR at turnover.