+1
And the steel rule method is actually better than a chain gauge:
1. a 12 inch steel rule measures over a larger number of links, and so can more easily detect small amounts of wear
2. a steel rule can measure wear that is other than 0.5%, 0.75%, 1%, or whatever wear increment the makers of the 'proper' instrument think it is useful to measure
3. if you use a 3 foot steel rule, and hang the chain from a peg, the steel rule method is far superior to the 'proper' instrument