Honestly I gotta disagree here. I mean sure, showing someone a problem makes sense, but relying on a tool to do all the convincing feels like a shortcut that could backfire. What if they don't understand what they're looking at, or they think you're just creating a problem to sell a service? You still need the words to explain it properly. Idk, maybe it's just me, but I've found that skipping straight to the demonstration without building that trust first can make people feel cornered. A tool is just a prop, it doesn't replace actually talking someone through the why and the how.

Cardboard's a solid choice for shims in a pinch, but if you've got access to composite shims they're way more stable long-term. I had to deal with a wall that was out by almost an inch once, layered in cedar shingles trimmed to fit. The key is to glue them in place before you screw the board up, stops any shifting while you're working. A thick coat of mud over the tape and a careful sanding job makes all the difference. Looks factory when you're done, no one would guess the framing was a mess.