Few thieves use sophisticated methods to get into homes. Very few pick locks or circumvent alarm systems; most simply open unlocked doors or windows, lift sliding glass doors off their tracks, use a stolen key, or push or pry open weakly defended doors, windows, and garages. Intruders prefer empty homes, visual obscurity, silence, easy entry, and quick exits. Your primary objective when planning home security, then, is to beef up your locks and latches, and maintain good security habits. Here are basic steps you can take to strengthen your home’s physical barriers. Click here for tips on maintaining good security habits that will further thwart baddies.

Lose Lousy Locks

Good locks are essential. Click here for our section on locksmiths, which describes various types of locks, how they can be strengthened, and how to find a good locksmith.

Set Up Some Surveillance

Dozens of device manufacturers and tech startups are clamoring for consumers’ home security business. You can buy something as simple as a single doorbell camera to a sophisticated full-scale security system that monitors all doors and windows, and scans for movement and heat signatures. You can install it all yourself for free or hire a handyman service to do it.

There’s now so much competition in the home security business that the cost of equipment and monitoring have collapsed. You can buy a doorbell camera for less than $150 and monitor it yourself via smartphone app, or pay as little as $100 a year for a company to monitor it 24/7—without the long-term contracts typical of the home security industry.

We discuss here what’s available to DIYers, features to consider, and costs. An important consideration when shopping is to focus on devices that are “Matter-compliant,” a new standard that allows gadgets made by different manufacturers to talk to one another, eliminating the need to buy all your stuff from one company.

While there’s some evidence that burglars tend to avoid properties if they notice the presence of cameras and other security systems, there’s scant proof that cameras help police identify and catch criminals. And because cameras can pose a threat to privacy and civil liberties, it’s worth considering the cost vs. benefits of using them.

Secure Sliding Glass Doors

The locks on sliding glass doors are notoriously flimsy—many doors can be lifted right off their tracks. If you have one, consider paying a locksmith to evaluate its vulnerability and, if necessary, install reinforcements.

With most models, one door is fixed (screwed or bolted at several points to the track), so you just have to worry about its partner. You can prevent a pry-bar attack with a broomstick placed in the lower track to prevent the door from sliding open. Aluminum “Charley Bars” mounted waist-high do the same job.

If both doors slide, secure them by drilling two 9/32-inch holes where their frames overlap at the top and bottom. Drill through the inside door’s frame and halfway into the outside door’s frame; then insert 1/4-inch bolts in the holes. This will prevent intruders from prying the doors open and make it difficult for them to lift them off their tracks.

To prevent burglars from lifting a sliding door off the track to open it fully, drill vertical holes through the overhead track every 12 inches or so. Drive screws into these holes just far enough so that the doors slide under their heads but can’t be lifted off the track. This technique will not work on some hollow frames.

Fix Your Windows

There are five common types:

• Double-hung (sash) windows open vertically; sometimes the top half is fixed and sometimes it’s not.
• Horizontal sliders are like small sliding glass doors.
• Casement windows swing outward and are usually opened and closed by a lever attached to a geared hand crank.
• Jalousie windows are a series of panes about four inches wide set in frames interconnected by levers.
• Fixed pane windows do not open.

Secure windows by making them resistant to being pried open. In addition, it should be difficult to open the window frame after a pane of glass has been broken. Most intruders are not keen on breaking glass.

Quick Fixes

The easiest-to-defeat type of window is the jalousie, since even when it’s locked its panes are easy to remove. If you have one that can be reached from outside, consider replacing it, adding bars, or attaching an alarm to it.

Casement windows, when closed, often withstand break-ins due to the locks on their frames and their hand crank mechanisms, which resist prying. Still, if you leave one open a few inches, someone can reach in and turn the crank to fully open the window. Make that more difficult by removing the handle, or cover the window with bars or an alarm screen.

Because locks on horizontal sliders are often flimsy enough to be snapped, consider auxiliary locks.

Double-hung windows are relatively easy to secure, but many commonly available locks are not effective. A simple way to secure them is to pin the two frames together.

Improve Glazing

You can make windows even more secure with impact-resistant glazing. Follow manufacturers’ instructions for mounting them, since temperature increases make them expand more than regular glass panes; if installed improperly, intruders can bash them in.

At considerably greater cost, you can have a pro replace particularly vulnerable windows with the type of materials used in car windshields, which is not difficult to break but is hard to remove.

Install Bars

Protective metal bars, whether decorative or standard prison issue, are the ultimate break-in deterrent. Most are fully welded on a semi-custom basis by local installers who do not sell them for do-it-yourself installation.

You can buy bar sets ($40-$100) that can be adjusted to fit your windows; they come in several heights and expand up to 42 inches wide. They won’t resist attacks as effectively as fully welded bars, but, properly installed, they’ll discourage all but the most determined intruders. Some hardware stores also stock fully welded window bars, although the selection is limited and may not be suitable for your windows.

Professionally installed, fully welded bars cost about $100 to $300 for a 30-inch-by-60-inch window if you get bars for several windows at one time.

Don’t Block Escape Routes

Metal bars on windows or doors, or difficult-to-remove locking devices (such as screws in window frames), pose hazards in the event of fire. Most building codes specify that any sleeping room without an exterior door should have an easily opened window. Window bars with hinges on one side and a lock on the other are risky because the keys can easily be misplaced. Hinged bars with an extended mechanical latch release are safer: No one outside can reach the release, but it can be easily operated by someone inside.

If windows are secured with screws, make sure all occupants know that in order to escape through the window they’ll need to knock out the glass, place a blanket or other padding on the bottom frame, and carefully climb out.

Block Other Access Routes

Intruders love unlocked attached garages. After entering the garage and closing the door, they can then bust into the house unseen and unheard.

Standard twist handle locks on overhead garage doors can be easily defeated. Electric door openers provide more resistance, but because even these may yield to a crowbar attack, it’s good to have a backup lock. One simple and inexpensive solution is to drill holes in the track on each side just above the closed door and put U-bolts or padlocks through the holes. This keeps the door secured only from inside the garage when the door is closed. The door can also be secured from the outside with a hasp and padlock.

In search of hidden entries, many intruders head to utility rooms and enclosed porches. Make them difficult to access. Plus, make sure a solid-core door with reinforced locks separates them from the rest of your house.

If someone could conceivably enter your attic from the outside, lock the attic hatch or door. Instead of glass, most skylights are now a thin plastic that is easily broken. Consider shatter-resistant glazing or adding metal bars.

Most window ACs can be removed easily from the outside or by pushing the unit in. The first precaution is to secure the partly raised window frame tight against the AC case by pinning or screwing the frames together. The easiest way to prevent someone pushing or pulling out the unit is to screw a piece of lumber to the top of the windowsill. You can improve the aesthetics by extending the board from one side of the frame to the other and painting it the same color as the sill.

Replace Weak Doors

Hollow wood doors can be easily punched through. Exterior doors should be solid wood or foam-filled metal. Doors should fit snugly within door frames, with no more than a 1/16-inch gap on either side.

The most secure model is a heavy-duty steel door in a steel frame with a high-security lock. A less costly step down is a metal-bar door installed a few inches outside an existing door. When set into a brick or concrete-block structure, defeating them is generally noisy and time-consuming. The simplest kinds of metal-bar doors, which are usually installed along with bars over the windows, make your place look like a prison. But some fabricators make attractive decorative ones, and a few custom-build them as individual pieces of art.

If you have an outward-opening door, make sure it has hinges with non-removable pins. Hinges should also be installed so that the screws attaching them to the door and frame cannot be accessed when the door is closed.

Click here for more advice on buying and installing doors, plus ratings of local suppliers.

Keep Landscaping in Check

Doors and windows hidden by garages, fences, and landscaping are attractive targets for intruders who prefer to invade unseen. If possible, keep areas around your doors and windows visible from the street, to your neighbors and from within your house.

If it’s impractical or unattractive to hack back your jungle, consider planting thorny bushes close to the house to keep prowlers away. Garden centers and landscapers can advise you on what to plant and give you help planting it. Click here for ratings of landscapers and landscape designers.

Large trees may provide access to upstairs windows or, more often, to a porch roof near a window. Consider pruning them. Click here for ratings of tree care services.

Fence It In?

A high fence is a double-edged sword: It can make it more difficult for an intruder to get in and out, but it also can hide a burglar. If you have a gate, keep it locked so an intruder knows the fence would slow his escape. Click here for ratings of fence builders.

Light It Up

Turning on an outside light will chase away all but the nerviest prowlers. Illuminate the entire exterior of your house or vulnerable areas, either all night or on a motion trigger.

Professional installation of a whole-house security-light system costs $1,000 to $3,000—and increases your electric bill. A do-it-yourself installation at one point of vulnerability may cost less than $250. Unsecured outdoor lights with outdoor sockets (which usually take reflector lamps) cost much less, but a careful intruder can remove the bulbs.

Place the switch for any outdoor light or lighting system intended to provide security in a convenient location away from the light. You won’t want to run downstairs to turn on a light when a prowler is breaking through a nearby door.