These are great. Has its limitations and still needs to be used intelligently I guess, but it's a very handy tool for quickly marking a centerline on small stock. I'm going to see if an artist's/draftsman's 2mm lead holder will fit into this tool, but for now a standard wood pencil in hex or round fits and works well, as do a couple of the cheapie Papermate mechanical pencils if you can use them gently and not break their small lead (the Sharpwriter and another which is a top clicker). I've not found a pen that fits well but the old clear hex Bic models might work. The top of the tool that grabs the utensil is flexible enough that you can easily squeeze and firmly hold it in use to keep it from backing out. The side notches are...a quandry. Useful idea, maybe useful in practice if you measure first and they suit your purpose, but they are literally identical on both sides and also don't match up with their stated dimensions. I didn't fully check those out on different widths of material so maybe there's one in particular that makes those accurate. Anyway, great tool in a cheap version that works well. Sturdy enough to endure a cluttered tool bag if need be but the handy magnet mount is a great and useful feature.