Maybe you could start off with a long string and then mark off its midpoint, the midpoints of the halves, and so on. Then you wouldn't have to cut a new string every time you want to measure something.
What, and use the same thing to measure stuff anytime you measure something? Like that's ever gonna catch on! Next you're gonna tell me to use my lower arm as a measuring stick!
There's also the concept of a story stick.
When working on a project where you need a bunch of things to be the same, you take a stick and mark on it at various points the dimensions you're using -- when working on a house, it might be things like the heights of outlet boxes and switches, the width and height of rough opening for doors, the height of window sills, etc etc.
Then, you just use the stick as the reference, using the marking for outlets to position all of the outlets instead of measuring the height of the floor in inches or millimeters or cubits or whatever each time. It's kind of like a measuring jig.
("Measure once, cut twice" is a superior methodology which has been unfairly maligned for generations.)