(What every entrance-door owner wishes they knew before buying a second smart deadbolt)
1. The Problem You Didn’t Know You Had
You just fell in love with a sleek smart lock for your new double-door entrance.
Then the contractor drops the bomb:
“Left leaf, right leaf—each needs its own lock, or the insurance company won’t sign off.”
Suddenly your budget doubles… plus another set of batteries, another app account, and another hole in your beautiful door.
2. What Building Codes Actually Say
In 90 % of countries a secondary “auxiliary” lock is required only for latching the inactive leaf; it does NOT have to be a full motorized smart deadbolt.
In other words, the right-hand door only needs something that:
- keeps the door closed,
- throws a bolt into the frame, and
- can be opened from inside in an emergency.
No Wi-Fi, no fingerprint, no circuit board—nothing “smart” at all.
3. Meet the “Slave-Lock” (a.k.a. Surface Bolt or Flip Lock)
Our Slave-Lock is a solid-brass, 30 cm vertical bolt that:
- mounts on the back edge of the inactive leaf,
- slides upward into the header and downward into the sill (classic “top-and-bottom shoot bolts”),
- connects to the main lock’s top & bottom “tongues” so one turn of your smart deadbolt throws THREE points of steel into the frame—top, center, bottom.
Result: The door set behaves like a fortress, yet you paid for only ONE smart lock.
4. How the Magic Happens (30-Second Install)
- Close the right leaf and mark two 6 mm holes—one in the upper jamb, one in the floor plate.
- Screw the slave-lock body flush with the door edge.
- Clip the supplied linkage rods to the existing top/bottom tongues of your main smart lock.
- Open and close once—rods self-adjust.
- Done. No cable, no battery, no app pairing nightmare.
Total time: Less than unpacking that second smart lock you almost bought.
5. Savings That Speak for Themselves
| Solution | Hardware Cost | Battery / Year | App Accounts | Install Holes |
|---|---|---|---|---|
| Two smart locks | 2× | 8 × AA | 2 | 4 |
| One smart lock + MS-SB100 | 1× + small addon | 4 × AA | 1 | 2 |
| You keep: | Money | Half the batteries | 1 less headache | 2 less holes |
6. Will It Match My Door?
- Finishes: Satin nickel, matte black, antique brass, PVD gold.
- Door thickness: 35–55 mm (includes long screws).
- Frame type: Wood, aluminum, steel, even glass-door headers with our shallow-floor plate.
7. Still Not Convinced? Here’s the Proof
- UL 10C 3-hour fire test passed—same rating as the primary lock.
- >200 kg side-load tested (equivalent to a grown man kicking the door).
- 10-year corrosion warranty on the marine-grade spring.
8. Quick FAQ
Q: Does the slave-lock auto-lock when I leave?
A: It doesn’t need to. Once the main smart deadbolt throws, the rods extend automatically. When you unlock, they retract. Zero extra steps.
Q: Can I open the door from outside if someone latches the slave?
A: No—and that’s the security point. Only an interior thumb-turn or your smart lock’s motor can retract the rods. No outsider can “credit-card” the slave.
Q: My old double doors already have two cut-outs. Can I retrofit?
A: Absolutely. Remove the dummy cylinder, cover the hole with our escutcheon plate, mount the slave-lock below. Works even if the prep spacing is non-standard.
Bottom line
Stop paying for circuitry you don’t need. Keep the convenience of one app, one battery set, one sleek keypad—and let the Slave-Lock do the quiet, mechanical heavy lifting.
Need sizing help, a bulk quote, or just want to say hi?
Email us: YiTechE@gmail.com (we answer within 8 hours, usually with drawings attached).
