Wouldn't It Be Adequate?

Last night we plotted the area for the backyard patio. The first angle we attempted to make using the pythagorean theorem (the "3-4-5 rule," according to the various things I read about doing this sort of stuff). That did not work so well, probably because we were using some sort of decorative (stretchy) ribbon that we found in our house four years ago when we took possession of it, instead of using some sturdier stuff. Long story short: we ended up eyeballing the thing and checking with a small square. Quick measurement of the resulting diagonals showed them to be about 1/4" off. That's good enough.