You can make something that works about as well as this pretty easily.
Put a ruler on the floor
Fold a piece of paper half twice so it will stand up at a 45* angle
Draw an Arrow in the bottom corner with the tip of the arrow right in the corner.*
Put the paper next to the middle of the ruler
Set your camera& tripod up so you get a nice 45* angle on this thingy and snap away
Nice and easy.
*I like to note stuff like which lens I'm using, what aperture, camera body, where I thought I was focusing (focus on 18inch mark, for example) distance from camera to target, etc. Most of that info is in the EXIF data with digital, but I find it faster to just read a slip of paper than to open the EXIF and search for what I want to see... and it works with film.