What is this yellow paint on bolts/clamps in the engine bay?

[keplaffintech]

Looking through the engine bay, I see yellow paint markings on bolts and various clamp joints, as pictured. What are these for? Are they anti-tamper markings or something?

 

[nhcowboy28]

More or less. It’s also to ensure if they work on stuff, they align things back to where they were for easy access next time.

 

[D.J.]

They are "Witness Marks" that are meant to be applied after the fastener is torqued.

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[fairmont1998]

"Counter measures" is what we called them in the Holden factory. Simply a quality check to make sure a process has been done. Sometimes by the operator doing the process, sometimes by a following operator as a second check.

 

[Grump]

"Quality Control" at the car factory I worked at. After torque or install you hit it with the paint pen. Sometimes different colours mean different things. It'll get double checked down the line and before it exits the factory by more QC employees.

In this case it proves the hose clamp was installed and those bolts were torqued to spec.

 

[Hockster]

Easy way to tell if a nut is backing off as well.