Edges: one formula for everything
The goal
To put any edge in place with one and the same formula, without spoiling anything else.
The buffer is like a hand: it holds one piece, you send that piece home and get back whatever lay there. Swapping just two edges is impossible, that is how the cube works, so the formula also swaps two corners. You can ignore this: the next swap puts them back.
The edge buffer: top right, sticker B. The target: top left, sticker D. The T Perm formula swaps them.
R U R' U' R' F R2 U' R' U' R U R' F'
How to put an edge in place
- Look at the sticker in the buffer and find the letter of its place. Say it is F.
- Do a setup: moves that bring the place F to the target D.
- Do the swap: the sticker from the buffer has landed in the right place, and a new one has come to the buffer.
- Undo the setup with the reverse moves. The edge is home, and everything the setup moved is back.
One edge, two stickers: different setups
What matters is exactly which sticker must land in the place, or the edge ends up flipped. That is why an edge has two letters.
L' swap L
Dw' L swap L' Dw
You do not learn setups: you work them out
Only L, Lw, D and Dw will do. R, U, F and B would disturb what the swap uses. Lw is the two left layers together, Dw the two bottom ones. The goal is always the same: bring the sticker to the top face, on the left.
All setups, to check yourself
Lw2 D' L2
Lw2 D L2
none
L Dw' L
Dw' L
L Dw L'
Dw L'
Lw D' L2
Dw2 L
Lw D L2
L'
Dw L
D' Lw D L2
Dw' L'
Lw' D L2
L
Lw' D' L2
Dw2 L'
D' L2
D2 L2
D L2
L2