But the op says they are constantly losing tape measures, so if they measure the gap one day and write it down, then come to cut the wood the next day, using a different cheapo tape............good luck to themDoesn't matter; they could even have the markings at random intervals completely unrelated to any world measuring system, so long as you use the same tape to measure the gap and measure the wood for cutting to go in it..
..but yes, it's nice to have a quality tape that has a good curvature so it'll self support as you reach it over a 4 metre gap, magnets on the hook, a screw cutout, and a decent return spring