The term 'Lash Marking' refers to a type of leather craftsmanship in which a pattern is created by cutting or burning the leather. The pattern is then filled with a contrasting color, usually black or white, to create a decorative effect. The term 'WELT' is a four-letter word used to describe a strip of leather that is sewn around the edge of a piece of leather to reinforce it and give it a finished look.