QSS & Walnut coffee table John Skipper (stoneskipper). The different types of joinery include tongue and groove, through tenons - double and singles, notches and square pegs. The tops of the tables and the legs are curved. Through tenons attach the legs to the tops - double tenons on the coffee tables (the single ones on the top.) The bottom cross pieces are connected to the double curved legs on the coffee table (the single curves legs on the end tables) with square pegs.