So you have inoculated 15 logs, and didn't label them because, how would you label them? You can't use a pen, it just doesn't work. And if you use a sharpie, 6 months down the road, it probably won't be there any longer.
This is why these aluminum tags are great. You can use any sharp tool to write into the soft aluminum. All you have to do then is nail the tags onto each log, and you are good to go. Each tag has two convenient holes in it.