Disassemble a hinge. Take half and line it up at a hinge mark, knuckles toward the outswinging door face and its straight side ⅛ inch from the edge. Trace the hinge in pencil onto the door. Then hold the hinge edge against the face of the door under the outline and draw a line under it. This will be a depth guide for your chisel.
Score through the layout lines with a utility knife. Be careful not to cut deeper than the guide lines. Carefully make a series of cuts, or kerfs, between the scored lines with a chisel and mallet. Sighting the chisel from the door face, tap lightly until each cut is at the depth of the guide lines. Hold the chisel bevel side down, and plow out the shards between the kerfs.
Once you've chiseled out the waste wood from the mortise, turn the chisel over—bevel facing up—and scrape the mortise clean and smooth. Check its depth and smoothness with a hinge leaf. It should rest squarely in the mortise and flush with the door edge. Finish the other mortises in the same way.
Tip: To hold the door upright on its edge, put "feet" on it—screw long, wide scraps of wood to the top and bottom ends, resting tight against the floor.
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Tape measure and folding ruler
Drill/driver with auger bits
Measure the width of your opening, jamb to jamb, in three places (top, middle,bottom) and the height, threshold to jamb, in three places. Note the largest of each and use these as a guide to buy the door.
2. KNOB SET
A set for a cylinder lock should include two knobs, a spindle, and two round escutcheon plates. For a mortise lock with a bolt, two escutcheons or a long backplate with a keyhole may be required.
Choose between a cylinder lock (a tube-shaped ;acthset with a lock on the knob) or a mortise lock (a rectangular set with a bolt and a skelton key). You can reuse an old lock, but a new mortise lockset might be worth the cost (less than $20) just for the mortise-cutting template that comes with it. Before buying a mortise lock, make sure the distance from the spindle hole to the keyhole matches the one on the backplate you choose, and that the lock body isn't too thick to fit your door.
You will likely need three to hanadle the weight of a solid-wood door or solid-core door. Many doors come with instructions that indicate the size and number needed.
5. LOCK INSTALLATION KIT
If necessary, for drilling for a cylinder lock. Tool companies make these kits, which come with two different hole saws that attach to a drill, along with a jig to guide where the holes go. Some kits also include a drill-mounted router bit and jig for carving out shallow mortises for the lock's faceplate and the strike plate.
6. WOOD SHIMS
To hold the door in its opening as you check the fit and mark for hinges.