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Corner Braces, Corner Irons, T-Plates and Mending Plates
Building MaterialsA table that racks, a drawer box coming apart at the corner, a gate that’s started to sag: most of the time the joint just needs a piece of steel across it and screws into good wood on both sides. The trick is picking the shape that matches the joint. Get the shape right and a small piece does the job; get it wrong and the biggest brace on the rack won’t help.
Which shape for which joint
- Inside corner brace: a bent L that sits inside a 90-degree corner, one leg on each piece. For the corner where a table leg meets the apron, a shelf meets its side, or the inside of a box.
- Mending plate: a flat straight strap that bridges a butt joint or a crack on one face.
- T-plate: a flat T for the spot where one piece meets the middle of another, like a crosspiece meeting a post.
Before any of them go on, pull the joint tight and square. A brace holds whatever shape you fasten it in, crooked included.
Small corner braces for furniture and cabinet repair
For furniture and cabinet work, WBC carries small inside corner braces (some labeled corner irons) by the size:
| Leg length | Sizes |
|---|---|
| Under 2 inches | 3/4 x 1/2 (black or zinc), 1 x 1/2, 1-1/2 x 5/8 |
| 2 to 3-1/2 inches | 2 x 5/8, 2-1/2 x 1/2, 2-1/2 x 5/8, 3 x 3/4, 3-1/2 x 3/4 |
| 4 to 10 inches | 4 x 7/8, 6 x 1-1/8, 8 x 1-1/4, 10 x 1-1/4 |
The first number is the length of each leg; the second is the width. Pick the longest legs the joint has room for, so the screws reach well past any split or old screw holes. The 3/4-inch braces go inside a drawer box; the 3-1/2-inch ones belong on a table apron or a bench. The long ones, 6 to 10 inches, are for big inside corners like a workbench frame or a gate.
Screws matter as much as the steel. Match the screw to the holes so the head sits flat, and pick a length that bites deep without poking through the show face of the wood.
Black heavy-duty braces, straps and T-plates
Then there’s the heavy black hardware, made to be seen. This is what goes on a cedar pergola, a barn-wood shelf on posts, a gate or an exposed beam, where the bracket is part of the look. National Hardware’s black braces are 1/8-inch-thick steel, a different animal from the small furniture braces:
| Heavy black hardware | Size |
|---|---|
| National Hardware corner brace | 2.4 x 3 x 2.4 in. |
| National Hardware corner brace | 4.9 x 3 x 4.9 in. |
| National Hardware corner brace, powder-coated | 6.8 x 3 x 3 in. |
| National Hardware corner brace | 7-1/2 x 1-1/2 x 1.6 in. |
| Black corner braces | 1.7 x 1.5, 8.25 x 1.5 and 12.25 x 1.5 in. |
| Black wide corner braces | 1.6 x 3 and 6.8 x 3 in. |
| Double corner brace | 2 x 1-1/2 in. |
| T-plate | 12 x 12 in., 3/16-inch steel |
| National Hardware black mending plates | 3 x 1.3 and 6 x 1-1/2 in. |
| National Hardware powder-coated mending plates | 20 x 1-1/2 and 24 x 1-1/2 in. |
Match the arm length to the piece you’re supporting: a long brace for a deep beam or post, a short one for a narrow rail. Thicker steel and a bigger profile are the starting point for a joint that carries weight, but size alone doesn’t tell you what a connection will hold; where a joint carries a real load, use the connector the plans call for, with the fasteners specified for it. The 12-inch T-plate in 3/16-inch steel is post-and-beam hardware, not a bookshelf part.
These take real fasteners. WBC’s black 1/4 x 1-1/2-inch lag bolts match the black hardware, and the lag has to fit the holes in the brace. The 20- and 24-inch straps are long enough to tie a joint together across a wide face.
Outside, think about water. Montana snowmelt keeps ground-level wood wet for weeks, and bare steel rusts there. For a gate or a post near the ground, look for an exterior-rated finish such as hot-dip galvanized, and fasteners compatible with the connector and with treated lumber.
A brace on a joint isn’t a shelf bracket
A corner brace stiffens a joint between two pieces that are already holding each other up. Hanging a shelf off a wall is a different job. If you do fasten an L to a wall, it goes into studs or solid masonry with heavy-duty fasteners, never into drywall with plastic anchors and never into mortar joints. A brace’s size doesn’t tell you how much shelf it will hold, so for a shelf that carries real weight, use a bracket made for shelving and fasten it into framing.
The Pick
For a loose table, chair or cabinet corner, use an inside corner brace with the longest legs that fit, from 3/4 inch for a drawer up to 3-1/2 inches for a table apron. For the look of exposed black hardware on a beam, gate or post, use National Hardware’s 1/8-inch black braces or the 12-inch T-plate with black lag bolts, and where the joint carries a real load, the connector and fasteners the plans call for.
Frequently Asked Questions
What’s the difference between a corner brace and a corner iron?
Often nothing: plenty of bent 90-degree inside braces are sold as corner irons, including some of WBC’s. Look at the shape. A bent brace sits inside a corner with one leg on each piece; a flat L lies across the face of a corner.
What are mending plates used for?
Bridging a butt joint, a seam or a crack on one flat face. Lay the plate across the joint so the screws go into sound wood on both sides, not into the split edge.
Can you use corner braces for shelves?
To stiffen the joint where a shelf meets its sides, yes. To hang a shelf on a wall, use a bracket made for shelving, fastened into studs or masonry with heavy fasteners. Small furniture braces aren’t shelf brackets.
What screws go with corner braces?
Screws that fit the holes so the heads sit flat, long enough to bite deep without coming through the finished face. Heavy black braces take lag bolts sized to their holes, like WBC’s black 1/4 x 1-1/2-inch lags.