Our dad was in the construction business. His company supplied steel door frames and hinges and the like for commercial construction. One activity that required full attention to avoid costly errors was measurements. If the door frame was half an inch too big, and it had to be sent back and rewelded, the building's progress was delayed, extra man hours were required, and some mistakes required buying more materials.

Construction workers might be told to build six windows three feet across, but in reality, in the finished structure, the windows will have slight variations in size - a half inch here or there. For the frame to fit the structure, the measurements have to be what is actually there, not what was described in the plans.

It's important to have a standard (mutually agreed upon size) inch or other unit of measurement. And these days, it helps to know how to translate from the metric system to the English/American system, and vice versa. If the manufacturer's hinge description is in centimeters, and the measurements you're given are in inches - you have to work a bit to figure out what to order.

It's important in supplying measurements to have some understanding of fractions, how to add 3/8 to 1/4, say. Dad pointed out that we go to school to learn how to do these kinds of calculations, but that a carpenter handles it more simply by just measuring with his tape or ruler and reads the total sum without having to calculate at all.

There are even simpler ways to measure in construction whereby the worker takes some cardboard, or a spare length of wood, marks precisely what is needed, and brings it in and says, I need a dowel this long.

Which kinds of measurement in which situations would be least prone to error? I think about that sometimes, and how that might also be relevant in other professions besides construction.