Thom Walker gave me this tip and I've had occasions to use it.

When the builder/applicator asks, “Why are you making a big deal over 1/8”?”

Ask him/her to stretch their arm as far as they can across an island countertop or the hood of their truck.
Now here is the fun part.
Place a $100 bill 1/8” beyond their reach and ask, “What’s the big deal now?”
As they stutter and stammer for a reply mine is, “You’ve left hundreds of these off of this project.”

Clients love the fact that they just got caught and you very clearly made this point.

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badair http://www.adairinspection.com Garland, TX 75042
Residential-Commercial-Construction-EIFS-Infrared Thermography
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