Welding and fabrication

1. The arc changes pitch when it's right: crackle to something steadier. My foreman said 'listen to it' in week two. The cert course never mentioned sound at all.

2. Porosity shows in the colour at the edge of the bead before there's a hole. I can pick it across a workshop and I can't tell you what I'm looking at.

3. You read how a section will pull off the thickness and the clamping before you tack it. Nobody with ten years on the tools would call that a skill.