Which tool is used to make watertight seams when installing sheet metal lagging on flat sheets or complex shapes?

• A. Pittsburgh machine
• B. Caulking gun
• C. Chalk line
• D. Tin snips

Answer: (A)

When you’re joining sheet metal lagging and need a watertight seam, you rely on a tool that actually forms and tightens the seam along the edge. A Pittsburgh machine is built for this purpose; it crimps and folds the metal edge so the two sides press together firmly, creating a continuous, weatherproof joint. This works well on flat sheets as well as complex shapes because the tool can be guided along different contours, producing a tight seal along the entire seam.

In contrast, a caulking gun applies sealant to gaps but doesn’t form the seam itself, so it can’t achieve the mechanical watertight joint that the Pittsburgh machine provides. Chalk lines are for marking layout lines, and tin snips are used to cut metal, not to seal or join it.