Heise method

Once you have built all 4 (possibly non-matching) squares, the next step is to match them, and then also orient the remaining edges. First we will learn how to do these as two separate steps, and then simultaneously.

Separately

Joining the 4 squares

If stage 1 is completed correctly, it should be possible to rotate all 4 squares to their solved positions. Below are some examples:

Orienting the edges

For this step, we classify edge orientation as correct, incorrect, or neutral:

You need to orient the remaining edges so that there are no incorrect edges. That is, you may have correct or neutral edges.

• Strategy 1 - simple swap

  	When a neutral edge in the front/middle position is swapped for an incorrect edge on top, the neutral edge can become correct, and the incorrect edge can become neutral.
  	By applying a series of simple swaps, it is possible to eliminate all of the incorrect edges.

• Strategy 2 - criss/cross

  When many incorrect/neutral edges are bunched together, the criss/cross maneuver can be an efficient way to re-orient them.

• Strategy 3 - reassigning the free column

  	By reassigning the free column first, the previous two strategies can be reused on a different column.
  	This configuration can be fixed by reassigning the free column, doing a simple swap, then returning the free column to its original position.
  	Reassign the free column plus criss/cross.

Simultaneously

Now we will learn how to do the previous two steps simultaneously. This is possible because each rotation of a square also has an effect on the orientation of the edges.

In the following table, the top row shows some cases solved in two steps, and the bottom row shows the same cases solved by orienting edges and joining the squares simultaneously: