I had a useful one some years ago. It used quite heavy leads. Probably just under 1/8" dia, (Don't know what that is in new money.) It was the type that had a built-in sharpener on the non-business end. With this pencil I could sharpen a lead to a needle point and with the lead protruding right out, it was great for marking between dovetail pins/tails.
Problem is, I haven't seen one for ages, nor the leads for them either. Not that it matters. I lost the sharpener ages ago!
I mentioned already that there is an article on Rods in this latest edition of GW. I don't use rods all of the time, but i do measure 'by reference' to the job, far more than I use a rule.