Pipe hanger spacing, do you trust the book number or what the old guys on the crew say?
Had a 6 inch steam line in Tulsa where the spec called for hangers every 12 feet, but the 30 year guy told me to go 8 and it took me an extra 6 hours to redo it. Half the crew said I wasted a day, the other half said he saved me a callback. Whose number do you actually go by when the spec and the veteran disagree?