4x4x4 Last two edges — flipped pair — Big-cube parity

Big-cube parity on the 4x4x4 to 7x7x7. The algorithm is Uw' R U R' F R' F' R Uw2 R U R' F R' F' R Uw' — 17 moves. The last two edges are each paired but sit the wrong way round, so a plain trade leaves one flipped. Two trades with a turn between them. This algorithm moves 11 edge pieces and 5 corners — fine during pairing, before the 3x3 stage.

The algorithm

Uw' R U R' F R' F' R Uw2 R U R' F R' F' R Uw'. Read it as the cube faces you: U is the top face, R the right, F the front. A prime (') is anticlockwise, a 2 is a half turn, a lower-case or w-suffixed letter turns two layers.

When it applies

Edge pairing. The last two edges are each paired but sit the wrong way round, so a plain trade leaves one flipped. Two trades with a turn between them. This algorithm moves 11 edge pieces and 5 corners — fine during pairing, before the 3x3 stage.

How it is checked

Every algorithm on this site is applied to a real model of its cube in the test suite and asserted to solve its case and touch nothing else. It was proved, not proofread. Practise it from the timer, or add it to a printable sheet.