Joinery describes the ways wood pieces are connected. The butt joint is the simplest and weakest, with two pieces meeting at a right angle and relying almost entirely on fasteners or glue. A miter joint uses 45-degree cuts to form a corner with hidden end grain, common in picture frames and boxes. A rabbet is a step cut at the edge or end of a board, while a dado is a groove cut across the grain and a groove is a similar channel running along it. The mortise and tenon is a classic strong joint in which a peg-like tenon fits into a socket-like mortise; a through-tenon is visible on the far side for emphasis, and a wedged tenon is split and wedged for permanent locking. A common rule sets the mortise width at about one-third the thickness of the rail.
Dovetails are the gold standard for mechanical strength and visual appeal. Their interlocking trapezoidal pins and tails resist being pulled apart. A through dovetail is visible on both sides, while a half-blind dovetail is visible on only one side and is common in drawer fronts. The angle is typically 1:6 for softwoods and 1:8 for hardwoods, and pin width is set slightly narrower than the tails for a tight fit. Routers with templates can cut dovetails quickly and uniformly, but hand-cut dovetails offer variation and a hand-made beauty. Beyond these, a biscuit joint uses flat oval wafers in slots to align edge joints, a dowel joint uses round wooden pegs in matching holes, and a pocket screw joint drives an angled screw into a pre-drilled pocket for a fast and hidden fastener. The Festool Domino system uses loose oval tenons, combining the speed of biscuits with the strength of mortise and tenon. A half-lap has each of two pieces thinned by half so they overlap flush, a bridle joint slots a tongue at the end of one piece into a corresponding open socket in another, and a finger joint, also called a box joint, interlocks square fingers for a strong and visually striking corner.
Modern wood glues are remarkably strong, and a properly clamped joint rarely fails in the glue itself. PVA, the common yellow wood glue, is clamped for about 30 minutes and reaches full strength in 24 hours. Hide glue is a traditional protein-based adhesive that can be reversed with heat and moisture, which is invaluable for antique restoration. Polyurethane glue expands as it cures, is waterproof, and fills gaps, while two-part epoxy is gap-filling, waterproof, and extremely strong. Clamps hold the work steady during cure, and woodworkers typically find that more clamps are always better than they think they need.