Hello,
I have a Starrett, Rabone and Moore and Wright which are all good. My best advice is to avoid those die cast zinc stocked things, which are flimsy, often not square and do not lock well. The rules can be poor too, either badly etched or stamped out, so the ends are deformed and cannot be trusted. The good ones are engineering quality and therefore, not cheap, but worth the investment as they will last a lifetime or more and more significantly, can be relied on. Marking out is important to get right, as you are aware, since errors inherent in a project right from the start are just frustrating. Do not skimp on a poor tool and you will be happy.
I would advise you to get a square with the rule graduated only in the measurement system that you actually use. The ones marked in both metric and Imperial are a pain as you cannot read right across the width of the rule, (for rules marked in both on the same sides) or you will end up having to flip the thing over and then find the graduations are from the wrong end so have to reverse the rule in the stock (for rules with metric one side and imperial the other) It is surprising how tedious this becomes. Besides, which ever system you use, you never use the other, so half the graduations are little better than decoration. I prefer Imperial, and all four edges of my rule on the Starret is marked that way. It is so much more convenient having fractional grads spread over many sides, keeping the markings less cluttered. The Moore and Wright is next best, superbly engineered, British and only slightly less convenient, having metric one side English t'other. At least the grads scan right across the rule. The protractor is bloody brilliant, though. Second hand examples still command high prices, but are worth it. Can be got in all metric, if that is your preference, but not all English. Starrett make all metric, too and Imperial or combos ( I think the combo should be avoided) If you can stretch to a new Starrett, I think you will be happy and never regret it and be safe in the knowledge that it won't have been abused.
Mike.
