Keyhole F2L
Keyhole First Two Layers or Keyhole F2L, sometimes named working corner, is a method that solves, normally, the first two bottom layers of the 3x3x3 cube. It is an efficient method for inserting mid-layer edges in the 3x3x3 LBL method. Its a slight advancement on the basic LBL method, because it requires fewer moves, as. well as more intuition.
Basic Idea
After the bottom layer cross, only three bottom layer corners are solved. The final corner is reserved as the keyhole to be used in solving the mid layer edges efficiently. To insert a mid layer edge using the keyhole:
You start, like in normal LBL from a cross, then you fill in three of the first layer corners. From that point you solve three of the middle layer edges using the empty corner position as the keyhole. For each edge do the following:
- First position the mid-layer edge in the U-layer such that it is above the centre matching the edge's up-facing colour.
- Using a D-Turn position the bottom layer so that the unsolved corner is directly below the mid-layer edge's position.
- Now execute one of R U' R' or F U F' to insert the edge.
After three corners and edges are solved you complete F2L by first solving the last corner and finally the last edge using the normal LBL algorithm: R U R' U' F' U' F or the mirror F' U' F U R U R' depending on the current orientation of the edge.
Alternative Procedure
An alternative way to do keyhole F2L is to use this order:
- cross (doesn't have to match centers)
- 3 corners
- 4 edges
- 4th corner
For that you will need three algorithms to solve the last pice depending on it's orientation:
List of algs...
