Wood doors that once fit perfectly may bind due to loose hinges, seasonal expansion of the door or, in rare cases, settling of the house. Fixes range from simple to complex, depending on the problem's extent and cause. If planing is required and you don't own a jack plane or larger power plane, consider renting one for the task.
If the hinges are loose, especially the top one, the door will likely bind near the top of the opposite jamb. Use a screwdriver to tighten any loose screws.
If a screw turns but doesn't tighten, replace the existing screw with a longer one that will penetrate the frame or go deeper into the door. Alternatively, plug the screw hole with small slivers of wood (matches, toothpicks and so forth) dipped in glue, then reinstall the screw (this approach is adequate only for lightweight interior doors).
If the door binds at the hinge side just before it closes, place a layer of noncorrugated cardboard under the hinges to shim them. Either fix one hinge leaf at a time in place, or remove the door and do all of the hinges at once.
To remove a door, support its weight on wood shims and then tap a nail into the hole under each hinge pin to drive the pin out a little. Tap the pins out the rest of the way with a hammer and screwdriver placed under the head of the pin.
If the door binds on the lock side and the hinge leaves project above the wood surface, deepen each mortise with a hammer and chisel. Cut the perimeter with the chisel vertical and its beveled side facing the mortise. Then make numerous consistent, shallow cuts spaced about 3/16 inch (5 mm) apart over the entire mortise, with the chisel held at a slight angle, bevel side down. Lay the chisel nearly flat to scrape out the small pieces and smooth the bottom of the mortise (see A).
If the door fits in winter but not in summer or in damp weather, when it expands, inspect its underside with a mirror for visible breaks in the paint or varnish. If the finish is not completely sealed, wait until the weather is dry and the door isn't binding, then apply a new finish. Use a paint pad that allows you to paint the bottom edge of a door without removing the door (sold at paint stores), or remove the door to brush it on.
For more severe problems with a door that doesn't seal properly, plane it. First test the jamb with a carpenter's square and spirit level to see if it's square and plumb.
Only if the jamb is out of square and you don't want to remove the casing to correct the problem should you plane the door's strike edge. Plane the edge near the top or bottom as needed to create a consistent gap all around the door. If the door binds near the handle, plane the hinge side.
If the jamb is square, close the door and set a carpenter's scribe to the widest gap dimension, or about 3/16 inch (5 mm) minimum. Hold it perpendicular to the door with its metal point against the jamb's edge and its pencil on the door's face, and draw a line parallel to the jamb along the entire length of the hinge side of the door.
Remove the door and stand it on its edge in a door jig to remove the hinges. To make a door jig, nail two triangular pieces of 2-by-4 wood to the wide edge of a longer 2-by-4. Space the triangular pieces about 2 inches (5 cm) apart. Then do the same with another 2-by-4. Stand the door on the 2-by-4s between the plywood, and tap in a shingle tip or other shim (see B).
Using the scribed line on the other side of the door as a reference, remove material from the edge with a jack (see B) or power plane. To remove an even amount, use long strokes from end to end. To achieve a taper, start planing where you need to remove the most wood. With each successive stroke, extend the cut more.
Finish with one or two light passes over the full length and chisel the hinge mortises deeper as needed. Install the hinges and hang the door to test the fit. When it's right, remove the door and hinges for sanding and finishing. Allow paint or finish to dry before you hang the door.