Second Layer Tutorial — Rubik's Cube (LBL)

Recap

The first layer filled in the four white corners — the whole white face done, each corner's side colors flush with the centers. The second layer fills the four middle edges (the ones with no white and no yellow), so each edge's two colors sit flush against their matching centers — and the first two layers are complete.

Notation is the same as before: R / L / F / B (the four side faces), U (the top), a prime ' is counter-clockwise, and 2 is a half-turn; this step uses two insert sequences — right insert U R U' R' U' F' U F, left insert U' F' U F U R U' R'. See Fundamentals if anything's unfamiliar; this step assumes your first layer is done (first layer tutorial).

Goal

Insert the four middle edges into the four middle slots one by one: each edge's two colors flush against their matching side centers. Get all four home and the first two layers are done.

Find the home first: every middle edge has exactly one

Middle edges carry no white and no yellow (white is in the first layer, yellow is saved for last) — that's how you spot them. Each middle edge has two colors, matching the two adjacent side centers whose shared middle slot is this edge's home. For example, a red-green edge belongs in the middle slot between the red center and the green center. Always find the home before placing an edge: read the two colors → find those two centers → the middle slot they share is the home.

Why the first layer holds: lift the corner, slot the edge, restore

Inserting a middle edge is a three-beat move: temporarily lift the solved first-layer corner that sits under the target slot out of the way → slide the edge in → put the corner back — the edge is home, the corner untouched. That's the whole trick.

Take the right insert U R U' R' U' F' U F: the first half U R U' R' lifts the DFR corner under the FR slot out to the top (lift the corner); the second half U' F' U F slides the edge in and returns the corner (slot the edge, restore). Done right, the edge is in and the first layer is intact — so when a corner pops out midway, don't panic; finish the sequence and it comes straight back.

This lift-and-restore pattern isn't unique to the second layer — the advanced CFOP "F2L" inserts corners and edges together in pairs, using the exact same mechanism. The second layer is just your first taste of it.

How to get the edge home

Once you know the home, every edge follows this flow: on the top layer find an edge with no yellow → turn U to align its side color with the matching center (the insert drops the edge into the slot directly below, so mis-align and it enters the wrong slot) → insert left or right by which way the top color points → leave any already-placed edge alone.

Once the side color is aligned, look at the top color: if its center is to the right, do the right insert (U R U' R' U' F' U F); if to the left, the left insert (its mirror U' F' U F U R U' R'). The four cases below cover every state an edge can be in. (The sequences are shown for the front-right FR slot; for any other slot, rotate the whole cube to bring that slot to FR and reuse them — see the first-layer page for why a rotation is enough.)

Recognition

Before turning anything, scan the top layer and ask each edge three questions: ① is it a middle edge? (no white and no yellow; if every top edge has yellow, a middle edge is stuck below — extract one first); ② is the side color aligned? (turn U to match it to its center); ③ does the top color point left or right? (→ left / right insert). Three answers and the handling is clear.

Pitfalls

The three most common mistakes:

• Wrong slot — inserting without U-aligning the side color. If the side color isn't flush with its center, the edge drops into the wrong slot; always align first (see the flow above).
• Stopping mid-sequence when a corner pops out — half an insert really does break the first layer; finish the whole sequence and the corner comes back (see "Why the first layer holds").
• Thinking you're done when no top edge is yellow — really a middle edge is misplaced below; extract one and continue.

Practice

Once all four middle edges are placed — both side colors flush with their centers — the first two layers are done. Drill it: scramble → cross → first layer → four middle edges, until it's smooth. Then move on to the last step — the top layer (yellow up, then permute).