In every frame the vertical pieces are called "styles" 2 (S S, Fig. 496), the horizontal pieces rails (RR). These constitute the framing itself, and in the example shown are filled in with panels (P P).
The pieces of wood forming a frame should be narrow, so as to be affected as little as possible by shrinking under atmospheric influence.
The inner edges of the styles and rails are grooved to the depth of about 1/2 inch to receive the panels, which should fit so tightly as not to rattle, and yet should be free to contract.