Would like some advice on general door locks?

Here's practical advice for choosing and maintaining door locks, based on real-world experience:
1. Lock Cylinder Selection

Check the Key for Security:

Simple keys (flathead/cross) are insecure → Thieves can pry them open in seconds with a wire.
Choose a serpentine or double-row key (C-grade lock cylinder); even professional tools will find it difficult to open.
Try it before buying:
If the key goes in and turns smoothly without jamming half a turn, the internal parts are not worn.

2. Lock Body Structure Considerations

Material You Can Feel:

Scratch the lock body with your fingernail; if it leaves a mark, it's a soft alloy; if it doesn't, it's good stainless steel.
If a magnet can't stick to it, it's genuine 304 stainless steel (rust-resistant and saw-resistant).

The Lock Tongue Should Be Strong Enough:

At least three latches: the main latch secures against the door frame, and the upper and lower auxiliary latches prevent prying through door gaps.
After closing the door, insert a bank card; if it can't fit through the gap, it's considered合格 (qualified/up to standard).

3. Smart Lock Anti-Scam Guide

Power-off Opening: A spare keyhole is required when the battery is dead → Don't buy purely electronic locks!
Anti-Hacking Test: Place a strong magnet against the panel; if the door opens → Return it! The clutch design is flawed.
Liveness Detection is Essential: If the fingerprint lock still recognizes your finger when it's wet/with tape on it → Replace it!

4. Installation Determines Half the Security

Long Screws Save the Day: Door frame lock hole screws ≥ 5cm, directly inserted into the wall's rebar → Thieves can't kick it open.
Reinforce the Door Frame: Add a steel plate to the corresponding position of the lock tongue (buy 3mm steel plate from a stationery store and cut it yourself).
Adjust Door Gaps: The door shouldn't wobble after closing tightly; the lock tongue should be fully engaged in the frame → Anti-pry plate.

5. Daily Maintenance Habits

Lock Cylinder Maintenance: Refill with pencil lead powder (graphite powder) annually for smoother operation and less dust accumulation.
Screw Inspection: Tighten all screws before the rainy season → Prevent moisture expansion and loosening.
Cleaning Smart Locks: Use alcohol wipes to clean the fingerprint sensor and a stiff-bristled brush to clean the keyhole.

6. Simple Methods for Upgrading Low-End Locks

Adding a Top/Bottom Bar to Old Locks: Drill holes in the top/bottom of the door and insert a steel bar → Thieves cannot pry open the door.
Anti-Theft Chain Alternative: Install a sliding latch (same as in hotels) on the inside of the door; it is more impact-resistant than a chain.
Blocking the Peephole: Add a rotating cover to the inside → Prevents wire from hooking the door handle.