Corner brace is a fairly broad term used to describe a wide selection of elements used in woodworking to decorate, strengthen and protect corner joints. These elements fall into two basic categories: external and internal braces. External corner braces generally serve as decorative finishes and as protection against impact damage. Internal braces serve more as structural supports to strengthen corner joints against compressive failure. External braces are usually made of brass or steel, while internal braces may be made of metal or wood.
The corners of timber constructions and furniture are particularly susceptible to impact damage and structural failure. The use of a corner brace can negate these weaknesses. Their use is a fairly common practice in the construction and cabinet-making industries because of this function.
Corner bracing may be applied in one of two ways. The first is the external brace, which is most commonly used in the manufacture of furniture, crates and cartons. These braces are used to either cover the corner only or extend along the edges of the flat faces between corners as well.
External corner braces are usually made of decorative metals, such as brass or steel, and often feature highly ornate embellishments or engraving. They typically consist of a triangular shaped plate bent down at 90° angles along two of its edges. Screws are used to attach the brace to the wood on all three sides, effectively covering and lending protection and decoration to the exposed corner. Although they serve the same purpose, external braces used on packing crates and heavy cardboard cartons tend to be utilitarian and plain. This type of corner brace may consist of no more than a simple shaped-metal tape attached to the box with adhesive or nails.
The second type of corner brace is the internal type that serves as a structural strengthening measure to prevent the corner joint from collapsing under structural loads or from impact or compressive forces. These braces are typically L-shaped metal parts or straight timber members that are screwed onto opposite sides of the corner joint. They are commonly used in the construction industry to strengthen corners in timber frame structures. They are also frequently used to strengthen the corner joints of furniture, such as tables and chairs.
One specific type of corner brace commonly used to strengthen table corners is the kerf brace. This brace consists of a domed plate with a hole in its center and two lips bent out at approximately 30° at either end. These lips have small projections on them that fit into a vertical kerf or groove cut into opposite sides of a table's apron. The lips are then screwed down onto the apron sides to lend additional support. A bolt set into the table leg passes through the center hole and is tensioned with a nut, pulling the two sides of the apron together and bracing the corner.