Letter F pattern lock
How to draw the letter F as an Android unlock pattern, step by step, on the standard 3×3 grid and on 4×4, with the security score PatternGuard’s analyzer gives each version.
The letter F on a 3×3 grid
The letter F can be drawn exactly on the 3×3 grid thanks to one Android rule most people don’t know: the stroke may pass over a dot you already used. That lets you go back over a line: in step 4 the stroke passes over dot 4 again.
- Start at dot 5 (center).
- Go to dot 4 (middle left).
- Go to dot 7 (bottom-left corner).
- Go to dot 1 (top-left corner), passing over dot 4 again.
- Go to dot 2 (top middle).
- Finish at dot 3 (top-right corner).
PatternGuard’s analyzer gives it 25/100 (Weak): 6 dots, 1 crossing, starting at the center.
Is a letter F pattern safe?
Not really. Letters are among the first shapes anyone tries: research on real-world patterns found that about 1 in 10 is shaped like a letter, often the initial of a partner or a child (Løge, 2015). If your name or your partner’s name starts with F, this is one of the first patterns someone who knows you would draw.
A stronger way to use the letter F
If you like the letter F, don’t draw it on its own. Adding 2 dots after it keeps the shape you remember but hides it inside a longer stroke: 5 → 4 → 7 → 1 → 2 → 3 → 8 → 6 scores 44/100 (Weak), against 25 for the plain letter F.
It’s still published here, so treat it as an example of the idea, not as a pattern to copy. The safest pattern is one of your own that doesn’t spell anything.
The letter F on a 4×4 grid
Stock Android uses the 3×3 grid; 4×4 shows up in some custom ROMs and lock-screen apps, and the simulator supports it. The letter F can be drawn exactly on the 4×4 grid thanks to one Android rule most people don’t know: the stroke may pass over a dot you already used. That lets you go back over a line: in step 5 the stroke passes over dot 9 again.
Order: 11 → 10 → 9 → 13 → 5 → 1 → 2 → 3 → 4
PatternGuard’s analyzer gives it 34/100 (Weak): 9 dots, 1 crossing, starting at the row 3, column 3.
Why some letters can’t be drawn exactly
Android’s pattern lock has three rules: at least 4 dots, no dot can be selected twice, and if the stroke passes over a dot you haven’t used yet, Android adds it automatically. Passing over a dot you already used is allowed, which is how letters like P, R or F can be traced exactly. On 3×3, shapes with a closed loop or three or more loose ends (like A, B or O) still need one line left out or one line added; the 4×4 grid has more room, but not always enough.