Making a Safe Lock for Double-Hung Window

Do you have wooden double-hung windows in your house that go up and down in a track?

If so, you may have lamented that although they provide good security when they are closed and locked, there is no way to lock them open only five or six inches for ventilation so you can feel secure no one can climb through.

Hardware stores sell several types of easily installed “venting locks” for double-hung windows, but the problem with them is that they can be disengaged manually from the outside by an intruder reaching through the open area of the window, and they are not very sturdy.

Here is a simple “do-it-yourself” way to very securely lock double-hung windows while ventilating that avoids the problem of removal from the outside. (The only tools you will need are an electric drill with a quarter-inch bit and a file).

1--From your local hardware store, buy enough 4-inch finishing nails so you have one for each window and a few spares. Also, buy the same number of small bar magnets (about an inch or so long). Round magnets are fine, too.

2--Cut the nails to a length of 2 7/8 inches. (If you cannot do this yourself, most hardware stores will be willing to do it for you. Avoid buying 3-inch nails because they are smaller in diameter). File off any sharp edges.

3--Place a piece of masking tape around the shank of a quarter-inch drill bit to mark exactly 3 inches from the point as a drill depth guide.

4--Close and lock the window.

5--At the upper-left or upper-right corner of the lower sash (about 1 inch in from the edge) drill a hole through the lower sash frame and into the upper sash frame, stopping when the edge of the masking tape is just in contact with the wood. This will leave a 3-inch deep hole.

6--Raise the lower sash to a height of about five inches above the sill.

7--Insert the bit into the same hole you just drilled into the lower sash until it hits wood on the upper sash at this new level. Drill a new hole into the upper sash at this point. Again, stop at the 3-inch masking tape line on the bit.

8--Place one of the cut-off nails into the hole, pushing it in far enough that the head is just below the surface of the wood so it cannot be removed manually.

With the nail in place in the quarter-inch hole, the window stays securely locked while allowing ventilation and cannot be removed by an intruder reaching in from outside. Use the magnet to pull out the nail to unlock the window. Do the same for more security when the window is fully closed as well.

For fire safety, be sure to attach at least one magnet for each window on the back of the window sash lock out of sight from the outside.

Gary Abrams is a general contractor who has written about home improvement for The Times for eight years. Comments and questions can be sent to P.O. Box 711, Thousand Oaks, CA 91319. Please include a self-addressed stamped envelope.

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Window Security

A cut-off nail inserted into a pre-drilled hole allows double-hung window to be locked in a position that is open wide enough for ventillation but not entry.