How to Shim a Door Using Wooden Wedges

Pry off the door casing with a pry bar if you are straightening the jamb for an existing door. If you are hanging a new door, the casing won't be installed yet.

Place a four-foot level on the jamb and adjust the jamb until it is perfectly vertical. If you are working on an existing door, you may have to pry out the top or bottom of the jamb with a pry bar. Prying out the top sometimes requires disassembly of the jamb if the horizontal jamb piece prevents the tops of the side jambs from moving.

Insert the pointed ends of two wooden shims behind the jamb at the point at which it is farthest from the stud. Insert the shims so they meet behind the jamb and push them together. Tap each one lightly with a hammer until they are wedged tightly in place without moving the jamb. Check the level of the jamb again.

Pound a pair of two-inch finish nails into the jamb, spacing them about two inches apart, so they penetrate the shims and sink into the stud framing the doorway.

Set pairs of shims along the jamb at 12-inch intervals in the same way, tapping them together until they are wedged in place. Secure with finish nails. When all the shims are in place, sink the heads of the nails with a nail punch.

Shim the top of the jamb and then the other vertical piece the same way. You may have to cut one or two of the jamb pieces with a handsaw to get them to fit. When all the jambs have been nailed off, use the handsaw or a utility knife to cut off the ends of the shims flush with the edges of the jamb.