I can't say I collect folding rules, other than the fact that I got one in Germany last year when I was over. I was amazed that all the carpenters and building professionals over there use them all the time, unlike the metal tapes which most us here. I got a 2m one which I now regularly use when surveying buildings, and to be honest find much handier than a tape in most instances. I'm on the look out for a better quality one as the one I got was a freebie and a bit flimsy .