In the past, whatever I used to label my tools rubbed off. But I’ve finally found a product that sticks to almost anything, can be removed easily and is inexpensive.
It’s called fabric paint and you can find it at craft stores. It’s non-toxic, cleans up with water, comes in a variety of colors and you can write with it like you would with a pen. In most cases the paint can be scraped off with a putty knife or razor blade.