End Grain

End grain is the surface exposed when a board is cut across its length, perpendicular to the grain -- you're looking straight down the open ends of the wood's fiber tubes rather than along their sides. That structure makes end grain soak up glue and finish far more than face grain or edge grain (part of why an end-grain butt joint glues poorly), but it also makes an end-grain cutting board -- like the boards built by the Cutting Board Designer -- the most durable, self-healing surface for a knife to work on, since the blade slips between fibers instead of severing across them.