A tongue and groove profile for a construction panel wherein the tongue protrudes and extends outwardly from a first edge of the panel to a head portion. A shoulder portion of the tongue has two radiused convex or concave sides which intersect and merge with the first edge of the panel. A groove is formed in a second edge of the panel and extends inwardly into the second edge forming a cavity. The groove has a head portion which extends into a neck which expands into a shoulder which has two radiused concave or convex sides so that the tongue will fit into the groove. The radiused sides expand to form an opening in the second edge of the panel. The tongue of one panel can fit in interlocking relationship into the a groove of a second panel to form a joint between the two panels.