A value scale is a handy tool that you can use to help you see and draw value. To use a scale to see value, hold it up so that the edge of the scale is next to your subject, squint your eyes, and then pick the value that matches best. Use the scale to check your drawing’s value in the same way.
I’ve made a downloadable value scale that you can print. It has a sliding scale on top and ten value steps on bottom. Download it by opening the link below and saving the image to your computer.