Fixing a 45 degree wood joint depends on the specific issue you are facing with the joint. If there are gaps between the two pieces of wood when assembled, one solution is to use wood filler or putty to fill those gaps for a seamless appearance. You can also consider applying glue along the joint before reassembling to strengthen it and create a stronger bond between the two pieces of wood. For more complex joint issues such as misalignment or unevenness, you may need to disassemble and recut the joints to achieve a better fit and alignment. It's important to take your time, measure accurately, and use appropriate tools when correcting a 45 degree wood joint for optimal results.