Doors get most of the attention when the subject is leaving the house at dusk, but windows matter too. A window that opens wide enough for a person to climb through is an exit, whether or not anyone thinks of it that way. A window stop is a small piece of hardware that limits how far a sash can open. Installing one is often a short job. Deciding whether you should do it yourself is the part that takes thought.

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Identify the window before you buy anything

Look at how the window moves. A double-hung window slides up and down in two sashes. A sliding window moves side to side on a track. A casement window swings out on a hinge. Each type takes a different kind of stop, and a kit labeled for one type may not fit another. Write the type on your shopping list before you go to the store, and bring a photo of the window to check the packaging against.

Check the height and the ladder

Ground-floor windows you can reach from inside, standing on the floor, are usually a reasonable do-it-yourself job. Upper-floor windows are a different question. If the install would need a ladder, a second person to hold it, or an outside reach, hire it out. A fall while installing a window stop is a worse outcome than a few days' wait for a handyman.

Check that the window is not your escape route in a fire

Some bedroom windows are required to open wide enough for a person to get out in an emergency. Before you install any stop, ask your local fire department or building office whether the window in question is one of those. If it is, the stop should be limiting, not blocking, and it should be releasable from inside the room without a key or tool. Put that question to whoever you hire, too, and ask them to show you the release.

Test it before you call it finished

After the stop is in, open the sash by hand and push it toward the stop. It should stop where it is set and not move further. Then check the release. Someone standing in the room should be able to clear the stop without tools, in the dark, in a hurry. If you cannot clear it yourself with the lights off, the install is not finished.

Decide who checks it each week

Whoever does the install, write down who will check the stop each week. The check is quick: push the sash, confirm it stops, confirm the release works. Name one person for that job, and write the name on the same page as the window type and the date of the install. A stop that nobody checks is only hardware.

Do it yourself when

The window is on the ground floor, the kit is labeled for your window type, you can reach the sash from inside on the floor, and the release is easy to find. Test it, write it down, and keep the instructions.

Hire it out when

The window is upstairs, the install would need a ladder, the frame or sash feels soft or uneven, or the window might be a required escape route and you are not sure. Ask the person you hire to explain the stop, show you the release, and leave you the instructions in writing.

The Window Stop Is a Screwdriver Job: Decide What You Fix Yourself and What You Hire Out