Red Seal Plumbing Practice Exam 2026 – Comprehensive All-In-One Guide for Exam Success!

The line around the nut on an acetylene fitting usually indicates that the fitting has a left-hand thread. This is important to know so that the fitting can be properly tightened and secured onto the acetylene tank without causing damage. Options A, C, and D are incorrect because a line on the nut does not indicate a right-hand thread, damaged thread, or standard thread. It is specifically used to indicate a left-hand thread in the case of acetylene fittings.