Ever find that you've gone through the trouble of measuring a space so that you can outfit it with bins, boxes or shelving only to find that your measurements weren't exactly clear enough to you while shopping for the containers and you ended up with ones that don't exactly fit?
Take a picture of the space. Enlarge it and print it out in black and white on regular 8.5×11" paper. Then write all the various measurements directly on the paper itself.
If you have any unusual molding, pipes or recesses, all the details will be right there for you to see and you can indicate all measurements accordingly.