Finding the 41 foot mark on a 53 foot trailer

Start at wherever the trailer kingpin is and measure back 41 feet and make some sort of mark. Works every time.

Then make yourself aware that some states use the middle of the axle group, and some use the center of the rear-most axle. And California for instance, the key words are 40 and rear-most axle

 

Unless you are on a bit of curved ground. Then you must calculate the offset of the tangent between the parallax of the obtuse triangle from the right angle of the rear most axles with regards to the natural curvature of the earth with a center point at right angles to the degree that the 5th wheel is tilted.

 

Start at the back of the trailer, measure 9 feet toward the front and mark it. That's your 41'.

 

That's the way I do it.

 

This is correct. However, there was no mention that the measuring device utilized must be certified (recent calibration) by the NIST

Furthermore, the mark must be approved by the appropriate CMV Enforcement division of the states where highway operations will be conducted.