Leadholder can be broadly defined as any durable instrument that is designed to hold and be refillable with consumable pieces of graphite so that the graphite can be conveniently used for drawing or writing. Within this definition there are subsets such as porte-crayons, mechanical pencils, and drafting leadholders. This website is primarily concerned with drafting leadholders, which are commonly called by draftsmen in the US as simply leadholders. (From “What is a Leadholder?“) —The Drafting Pencil Museum (Leadholder.com)
Okay, maybe I’m not quite that geeky, but I still enjoyed the site.