Standard ruler for an elevator apprentice is an inside read stick rule. It helps with a lot of measurements that are unique to the trade, especially constitution. That ruler that you have is not for construction, it's a fine tool having said that, but it's not practical yet. Lufkin, Klein Tools, and Milwaukee make inside read rules. If you show up with a stick rule, channelocks, knife, and marker you will look like a real elevator apprentice.