Whereas case joints join boards end to face, frame joints are primarily concerned with joining end to edge. Many design options are available to allow you to produce strong joints that can overcome the inherent weaknesses of end grain to long grain joints.
Frame-and-panel construction techniques were developed as a way to compensate for wood movement. Wood has a propensity to expand and contract the most in the direction of the growth rings (when viewed from the board's end). This movement is most often twice the amount of movement across the grain lines. Therefore any large board, whether composed of a single board or of multiple smaller boards joined together, will exhibit a considerable amount of expansion from edge to edge. Projects that are composed of large boards joined together will frequently experience joint failure due to the natural wood movement.
By constructing a frame around a floating panel, the panel can expand and contract safely within the confines of the frame, and the frame will experience only minimal fluctuations due to the narrow boards used for frames. Whereas traditional frames were used panels primarily for their practicality, many of today's panels also add a considerable amount of visual appeal to the frame.
Frames are primarily used as components in case construction, and can be found serving as case sides, back, top, doors, and drawer-fronts. Frames are broken down by their primary use:
A face frame is applied to the exposed outer face of a case to add visual detail, hide raw wood edges, stiffen and reinforce, and to provide edges and support for doors and drawers. The basic face frame is composed of a vertical stile along either side, and a horizontal rail across the top and bottom. The rails always run between the stiles, like rungs in a ladder, and not the other way around. To remember which is which, think of a horizontal railing at the edge of a balcony, or the fact that stiletto shoes have vertical heels.
A web frame is usually an internal element used to support internal case components like drawers, and to provide internal separation of components. Web frames still have rails that run horizontally across the case, but the stiles that run from the front of the case to the back are referred to as runners. These runners are located between the rails, which is the opposite of face frame construction.
Though the basic frame has two stiles and two rails, more elaborate frames can be constructed by adding more rails, or additional vertical members called mullions or muntins.
Horizontal rails and vertical stiles are sometimes embellished with various moldings. Alternately, vertical stiles can be embellished with various curves, ogees, and beads to produce a Greco-Roman column appearance.
The following joints are classified as frame joints: