Master these three “building block” joints and you’ll have the confidence you need to machine dead-on, snug-fitting joints for any number of woodworking projects. Rabbet: A two-sided, open-ended recess that runs along the edge or end of a board. Dado: A square-sided, flat-bottomed recess that runs across the grain. Groove: A square-sided, flat-bottomed recess that runs with the grain.