A warped cabinet door can cause numerous problems. Warping generally occurs when there is a water source nearby, such as a sink. The door soaks up the moisture in the air, this moisture causes the door to warp. A warped door will generally not close correctly. Two types of cabinet door warping exist, centerline and twisted. Centerline warping occurs when the warping occurs along the door in a length or width-wise fashion. Twisted warping occurs when the corners of the cabinet door twist away from one another.
Remove the door hinge from the cabinet by loosening the screws that secure the hinge to the cabinet.
Attach the two L-brackets on opposite corners of the door using screws and a power drill. Place a screw in each hole of the L-bracket and fasten the brackets to the door using a power drill.
Measure the size of truss rod needed by measuring between the two L-bracket mounting points. Measure the length of the threaded insert. Subtract the total distance between the L-brackets by the length of the threaded rod. Subtract an additional 1/2-inch for adjustment. Divide this number by two. This will give you the length of the two truss rods.
Cut the truss rods to the appropriate size using a hack saw.
Place each truss rod into the hole on the L-bracket and tighten the nut on the side using a ratchet and socket. Insert the threaded rod between the two truss rods. Thread the threaded rod into each truss rod.
Tighten the threaded rod using a wrench until the two corners of the door are pulled together enough to eliminate the warp.
Re-attach the door to the cabinet using a power drill.