Steel L Corner Brackets 3"x3"x1.5" (8 Pieces)

I used these heavy-duty 90° brackets on the inside corners of my 2x4 desk frame to reinforce the joints and keep the frame rigid.
 
They’re an easy way to add extra strength anywhere two pieces of the frame meet at a 90° angle, without adding a bunch of bulky framing underneath. I paired these with flat mending plates in other areas of the frame to make the entire desk feel much more solid.