In most cases having a crooked door means that it no longer closes smoothly. One edge rubs and it makes it hard to close or open the door. The last-ditch effort fix for the problem is to remove the door from the hinges and sand away at the trouble corner. This is guaranteed to fix your problem but requires a lot of work.
You have to remove the door, sand the edge, put the door back to ensure it is fixed then go through the process of reapplying the finish. These steps below can alleviate all this.
Screws always seem to find a way to wiggle loose over time. Look at the door top to bottom and determine where the door is rubbing. If the door rubs or sticks at the top or bottom, your problem could be as simple as a lose hinge. First look over the door and determine if it is rubbing at the top or the bottom. It if rubs at the top of the door, loosen or tighten the top hinge to move the door about an 1/8 inch. Do this on the bottom hinge if the door rubs near the bottom.
Pro Tip: Use a screwdriver when tightening screws in your hinges. Do not use a drill as you can easily over tighten the screw and strip the screw or bore a hole in the door by mistake. If you already have a stripped screw, remove it. Using a screwdriver or pliers you can usually remove the stripped screw. Replace it with one longer than the one that was there originally to ensure it catches.
SHIFT THE FRAME
After you have adjusted the hinges you can also try shifting the frame itself. Using a 3-inch screw, drive it through the frame and the door jambs. You will be attempting to pull the jamb further into the wall, if it has any room to move. This will not be a big adjustment if the door has been properly installed, but it can give you the minute move you need to have your door working properly again. Cover the screw hole with a calk or liquid nails to hide it and apply the finish already on the frame to conceal it.
SAND THE DOOR
This should only be done if the other steps have failed to properly realign the door with the frame.
Step one: Use a pencil while the door is on its hinges and mark the exact spots where it is rubbing, make sure to mark the entire area that rubs. If you have trouble marking on the door, apply masking tape on the edge first and then it will be easy to mark. Mark the door where it makes contact then mark a line 1/8th of an inch along the edge. You will need this in later steps.
Step two: Remove the door. Take the door off the hinges so you can get to the edges properly. Look at the weather and other factors to decide when exactly you want to do this because the door will be off for a few hours.
Note: This is a perfect opportunity to refinish your door as you will have everything you need to do so. If you wish to refinish your door remove the doors furniture when you take down the door. DO NOT DO THIS until you have fixed the door first though as at the end you will need to rehang the door to make sure it closes and opens properly.
Step three:Sand the door. Using a belt sander (which is faster and easier) or a hand sander begin the process of removing the extra material that is causing the door to stick. Using a low grain sandpaper, 50 grit, begin to sand away at the edge. This grit will take away a lot of material so be mindful of that. Work slow to ensure you are removing just enough. You can always go back and remove a little more if needed but you cannot add if you remove too much. When you have removed halfway to the line you marked a 1/8thinch away, switch to an 80-grit paper. This is a much finer sandpaper which will make a much smoother surface. Finally, when you are just about at the line switch to a 120-grit paper. This will create a fine surface for you to reapply the finish in later steps. Be mindful if you are using a belt sander that it will create very sharp edges on the door. Remove them by using the 120-grit paper and hand sanding those edges so they are somewhat beveled, rounded as is the rest of the doors edge.
Step four: Check your fitment. Hang the door back in place and see if it still rubs or stick anywhere. Don’t be surprised or discouraged if it does. You may need to do this process two or three times to get it right. There should be about an eighth inch gap between the door and the frame. Be careful not to remove too much material and to not create an indentation from sanding too much in one spot.
Note: Moisture can cause the door to swell or shrink, which can cause the fitment to be off. If you fix the door but don’t complete this last step, it is only a matter of time before you have the same problem or worse.
Step five: Re-varnish the door. Varnish does a lot more than make the door look nice. It protects it from the sun and the moisture. Moisture will rot, warp and eventually destroy your door. Varnish keeps the moisture from moving in or out of your door, preserving it and making it last much longer. If any spots begin to rub all of a sudden ensure they are properly coated in varnish, stain or paint.