Installing a Double Cylinder Deadbolt in Monrovia

How this works in Monrovia

Fitting a double cylinder deadbolt is mostly standard door work with a few extra details. The door needs a 2-1/8-inch bore through the face and a 1-inch bore in the edge, a backset of 2-3/8 or 2-3/4 inches, and a thickness the lock supports, usually 1-3/8 to 1-3/4 inches; thicker doors need an extension kit. The interior cylinder sits farther out than a thumbturn, so we check clearance for curtains, door stops and security screens. Both cylinders are keyed alike, and high-security options from Medeco, Mul-T-Lock or ASSA Abloy add restricted keys that limit copies of the one key everyone depends on. The strike matters just as much: a box strike with 3-inch screws into the framing. We finish by testing from both sides with the key and agreeing where the key will live. If the glass sits too close to the bore or the stile is narrow, we explain the options before we drill, so nothing gets cut that cannot be undone.

Work included on a typical visit

• Double cylinder deadbolt installation on glass-panel doors. Wood doors with decorative lites, French doors with wide stiles and doors with small windows near the latch are all candidates. We assess the glass distance, mark and drill with a jig, fit both cylinders and test the throw into the strike. You see the lock work from both sides.
• Keying, spare keys and the key plan. Because one key does everything, how you store it matters as much as the lock. We suggest a spot near the door but away from the glass, and a spare in a separate place. For households with kids or older relatives, we plan more carefully so nobody has to hunt in an emergency.
• Thick doors, French doors and narrow stiles. Standard double cylinder deadbolts expect a 2-1/8-inch bore, a stile wide enough to hold it and a door thickness around 1-3/8 to 1-3/4 inches. Thicker doors need an extension kit, and narrow stiles need different hardware entirely. We measure first, then choose a lock that fits instead of forcing the door to adapt.
• Strike, jamb and frame reinforcement. A glass door is often weaker at the frame than at the lock. After installing the double cylinder, we fit a box strike with 3-inch screws into the framing, check the hinges and look for split wood at the strike. The deadbolt is only as strong as what it lands in.
• High-security and restricted-key double cylinders. Where one key controls the whole door, losing control of it is costly. Medeco, Mul-T-Lock and ASSA Abloy make heavier double cylinder deadbolts with restricted keyways, so copies need your authorization. We install them where the property justifies it and keep a record of the key card.

How Monrovia shapes the job

In family neighborhoods across Monrovia, kids, guests and busy mornings make a key-to-exit lock hard to live with. Children can't always find or turn a key, and visiting grandparents have never seen it. For the front and garage-entry doors we recommend single cylinders. A double cylinder can work on a detached garage door or a storage room where nobody needs a quick way out.

Apartment tenants in Monrovia often ask about double cylinders after a break-in on a balcony or glass door. In a rental unit, the main entry must keep working deadbolt hardware under California law, and tenants need to leave without a key in an emergency. We usually recommend reinforcing the strike, protecting glass and asking the landlord to approve any lock changes. Landlords can call us to remove an unauthorized double cylinder at turnover.

Hillside and foothill homes near Monrovia face wildfire evacuation risk and sometimes steep exterior stairs, so a quick exit matters. Smoke and darkness make the seconds a key hunt takes dangerous. A double cylinder on the main exit is a poor trade. We recommend a standard deadbolt on main exits and keep any keyed-both-sides locks for outbuildings that aren't part of an evacuation route.

Example situations

• A landlord in Monrovia owns a duplex. After a break-in through a rear door's glass, he asks for double cylinder deadbolts on both back doors. We explain that tenants must be able to leave quickly without a key, and that heavier single-cylinder deadbolts with long-screw strikes address the break-in better. We install those, and he arranges laminated glass for the panes.
• A 1920s Craftsman near Monrovia Public Library in Library Park has a front door with nine small glass panes and a thumbturn deadbolt six inches from the nearest pane. The owner asks for a double cylinder. We explain that this is the home's main exit, so a lock needing a key to leave conflicts with exit guidance. We install a strong single-cylinder deadbolt with a box strike instead, and she calls a glazier about laminated glass for the pane nearest the lock.
• A homeowner installed a double cylinder deadbolt years ago and keeps the key in the lock whenever someone is home. We point out the contradiction: a key sitting in the interior cylinder is exactly what a hand reaching through broken glass would turn. She chooses a single-cylinder deadbolt and laminated glass for the nearest pane, which solves the key problem and the glass problem.
• A bungalow has a brass mail slot cut into the front door about eight inches from the deadbolt's thumbturn. The owner has read that a hooked wire fished through a slot can turn some thumbturns. A double cylinder would solve it but trap the household. We suggest sealing or relocating the slot, using a catch box, or mounting the deadbolt higher, and keep a normal thumbturn on the door.

From your call to the finished job

1. Talk through the door and the reason. Before we drive out, we ask three things: which door, how far the glass is from the thumbturn, and whether this is the way out in an emergency. Those answers tell us whether to bring a double cylinder, a single cylinder or both, so you can choose on site.
2. Check exits, glass and the people involved. This step separates a sound installation from a bad one. We confirm another exit exists, count the people who'd need to use it, and talk through the key plan. If we recommend against the lock, we say so before any drilling begins.
3. Measure, quote and choose the hardware. With measurements in hand, we confirm the stile can hold a 2-1/8-inch bore, the thickness suits the lock and the finish matches your hardware. We quote the lock, the strike reinforcement and any keying before we start, and you can decline.
4. Prepare the door. We use a drill jig to cut the face and edge bores square, protecting the glass and finish with tape and padding. If the door is already bored, we clean and check the holes. A crooked bore makes the key bind, so we take care here.
5. Fit both cylinders, key them and set the strike. Mounting is simple: the lock body, two cylinders and two through-bolts. The care is in alignment, so the key turns freely from both sides and the bolt slides into the strike without touching. We adjust the strike until it does, then confirm the screws bite into framing.
6. Test the lock and plan the key. The visit ends with an actual drill: door locked, key at the planned spot, you walking from the far side of the room. If that feels slow, we rethink the plan or the lock. We hand over keys and note the keyway and brand for your records.

Pricing factors

• Lock grade and brand. The lock itself is the first line of the quote. A solid mid-grade double cylinder suits an outbuilding, while a Grade 1 or restricted-key unit suits a higher-risk entry. We quote the specific model so you can compare it with a different grade.
• Door prep and thickness. A door already bored for a 2-1/8-inch deadbolt costs less to prepare than one that needs both bores cut. Thick doors need extension kits. Glass doors take extra care with masking and jig work. We measure before quoting so the prep is included.
• Glass protection you add separately. Laminated glass, security film and grilles aren't part of our lock work. Glaziers and window-film installers handle them, and they have their own costs. We install the lock and strike, and we can tell you what to ask those trades for.

Every job gets a clear quote before any work starts. Call (951) 903-3193 with the details and we'll tell you what to expect for your situation in Monrovia.

What to do before we arrive

• Tell every adult in the household, and any regular visitors, where the key lives. A babysitter, a house guest or an older relative who has never seen the lock should be shown on arrival. A note taped inside a cabinet door can help, as long as it isn't visible from outside.
• If you rent, don't swap in a double cylinder without written permission. Many leases restrict lock changes, and landlords carry exit and liability concerns of their own. Ask about reinforcing the strike or protecting the glass instead; those requests usually meet less pushback. Keep any approval letter with your lease.
• Review the setup every year. Kids grow, guests come and go, and keys get moved. Walk through the exit drill again, check that the spare still works and make sure the key hook is where you left it. A small annual check keeps the lock from turning into a hazard.
• Measure the real distance. Picture an arm reaching through a broken pane and see whether it can touch the thumbturn; if it can't, a double cylinder adds nothing. Measure from the nearest glass edge to the thumbturn, and from the glass to the door's far side. Tell us both numbers when you call.

Common errors that cost time and money

• Buying a double cylinder deadbolt online without checking the door. The stile may be too narrow, the thickness may be wrong or the glass may leave no room for the bore. Returning a lock is cheaper than repairing a damaged door. Measure first, or have us check before you buy.
• Giving out one key and no plan. A single key hung on a nail that only one family member knows about leaves everyone else dependent on that person. Spread the knowledge: everyone who lives there needs to know where the key is and how to use it.
• Skipping the strike. People focus on the interior cylinder and leave a thin strike held by short screws. A hard kick pops a short-screwed strike out of the jamb, and the double cylinder never gets a chance. Fit a box strike with 3-inch screws into the framing at the same visit.

Reaching Monrovia

Monrovia is about 44 miles from our San Bernardino base, roughly 48 minutes in light traffic via University Parkway to SR-210 West. When you call, you get an arrival estimate based on where the technician is and the traffic at that moment.

Our path into Monrovia depends on where the previous job wrapped up. Sometimes that's a straight run via Huntington Drive; other times it's surface streets the whole way. Either way, you get a heads-up call when the technician is close.

About Monrovia: The Aztec Hotel on West Foothill Boulevard, designed by Robert Stacy-Judd with Mayan Revival ornament, opened on Route 66 in 1925 and was listed on the National Register of Historic Places in 1978.

New or replacement locks in Monrovia?

Call (951) 903-3193 and tell us which doors and what kind of hardware you have in mind. If you already bought the lock, keep the box handy so we can check it fits the door, and we'll quote the install before any work starts.