Lesson 3 · ~15 minutes · needs your cube

F2L: The Four Doors

You called it: F2L. This is the longest stage of the solve and where the gap between 1:30 and sub-60 lives. The whole of F2L — all 41 named cases — reduces to four short inserts. Learn the four today; everything later is just steering pieces toward them.

The shift: pieces → pairs

Your old method almost certainly solved the first two layers in two passes: four corners, then four middle edges — eight separate lookups, each with its own pause. F2L batches them: each of the four slots takes its corner and edge together, as one pair. Four lookups instead of eight, and every insertion is 3–8 moves. Same total work, half the transactions.

Everything below assumes the standard frame: white cross on the bottom, and the slot you're solving at the front-right. For any other slot, rotate the whole cube (y / y') until that slot is front-right — the four doors below then apply unchanged.

Why triggers don't break the cross

One fact makes F2L legible. On top of a finished cross, U is the only free move — it touches nothing solved. R and F each disturb exactly one cross edge (DR and DF respectively). So every insert is a transaction: the opening R borrows the DR cross edge — parking it in the empty slot — some free U moves happen on top, and the closing R' pays it back. That's why F2L triggers always come with balanced turns (R … R', F' … F): they're borrow/commit pairs. Nothing to memorize there — but it's why you can turn fast without fear.

The four doors

With the pair's two pieces in the top layer, there are exactly four "easy" states, and each has its own door into the slot (case list: Ruwix F2L). Two are split (corner hovering over its slot, edge waiting across the top) and two are made pairs (corner and edge already joined, sitting beside the slot). Within each type, the corner's white sticker tells you which hand:

Door	Recognize (front-right slot)	Type
R U R'	Corner over its slot, white facing right; edge waiting at the back of the top	Split
F' U' F	Corner over its slot, white facing front; edge waiting at the left of the top	Split
U R U' R'	Made pair along the top's right edge, white facing front	Made pair
U' F' U F	Made pair along the top's front edge, white facing right	Made pair

Notice the structure: the second column of each pair is the first mirrored through the slot's diagonal (R-hand ↔ F-hand). And the made-pair doors are just the split doors with a U-alignment prepended. You are learning two triggers and one principle, not four algorithms.

Don't try to memorize the "recognize" column from prose — the drill below puts the real thing in your hands, which is where recognition actually forms.

Hands-on: the setup-solve drill

To manufacture any case on demand, apply the inverse of its door to a solved cube. The displaced pair lands exactly in the case position (with realistic junk in the slot); solving it back to a full solved cube is automatic verification — the feedback loop is built into the puzzle.

Level 1 — manufacture and study (do today)

From solved, apply a setup, stop and look — where is the corner, where is the edge, where does white face? — then solve through the door. Cube returns to solved = pass. Cycle all four until recognition is instant:

To practice	Set up with
R U R'	R U' R'
F' U' F	F' U F
U R U' R'	R U R' U'
U' F' U F	F' U' F U

Level 2 — shuffle (this week)

Same setups, but add 1–3 random U turns after the setup. Now the pieces aren't door-aligned: find them, use free U moves to rebuild a door state, insert. Pass = solved except possibly a rotated top layer (one U away). This is where the U-alignment principle becomes reflex.

Level 3 — real solves (goal for next session)

Scramble. Cross on the bottom (Lesson 2 rules), then solve all four slots as pairs — dead slow, no timer, narrating to yourself which door each pair took. When a pair is in some state you can't read yet, poke at it with R U R'-family moves until both pieces are on top and a door appears. That improvisation is intuitive F2L in embryo; next lesson makes it systematic.

Check yourself

Homework (before next session)

Four-doors drill daily — Level 1 until instant, then Level 2. Five minutes; keep 2–3 bottom crosses (Lesson 2) in the same sitting.
Two Level-3 slow solves by next session — completion, not speed.
Still owed: the Lesson 1 diagnostic report and the cube order status. F2L is now underway by your call, but the diagnostic still decides how much last-layer re-teaching Lessons 4–5 need.

Report back — start your next session with this

Check items off as you complete them (they persist between visits), then tell your teacher:

Level 1: all four doors recognized and solved without reference, 3+ days Level 2: shuffle drill passing (U-align without hunting) Level 3: two full slow solves — cross + four pairs Delivered the Lesson 1 diagnostic stall report New cube ordered / arrived (say which)

Primary source

J Perm's F2L page — the consensus-best F2L instruction; it routes to his beginner F2L video, worth its eight minutes before your first Level 3 solve. Written case reference: Ruwix F2L.

Questions — a case that fits no door, whether to learn back-slot inserts without rotating? Ask your teacher. · Course home · Four Doors card · Notation · Glossary · Lesson 2