Clock: flip methods and 7-simul

The Clock is solved when every dial on both faces points to 12. Pins couple groups of dials to the wheels; moving a pin changes what the next wheel turn affects, not the readings by itself. A wheel turn changes both faces, so finishing a visible side without tracking the back is not enough.

Read each face as a grid from its own viewing side. In scramble notation UR, DR, DL and UL select corner pin configurations; U, R, D, L and ALL select larger dial groups. A signed amount says how far the wheel turns, and y2 flips the puzzle. This wheel notation is not a complete fingering prescription for paired simultaneous turns.

Readings wrap around the clock face: adding a full revolution changes nothing. To bring a dial to noon, turn by the opposite of its reading; when moving a group, track differences between the affected dials rather than re-reading each from scratch. The dial lab lets you apply wheel turns and inspect both faces, and computes a checked wheel-turn solution. That solution is not labelled a 7-simul memo.

Work on a visible face first, then flip the puzzle and solve the other while preserving the first. Align groups relative to a reference dial before moving them together to noon. The shared corner readings constrain both faces: redoing a finished group with the wrong pins can undo work on the back. Learn the pin transitions slowly before trying to turn wheels faster.

In a flip approach, keep a consistent front grip and use the same reference dial while aligning its groups. Check the centre and edge dials as well as the corners; matching corners alone does not solve a board.

After flipping, read the back in its own grid orientation. Preserve already-solved groups on the first side by choosing the appropriate pin settings, then check both complete boards before stopping.

No-flip 7-simul reads both sides during inspection and executes simultaneous wheel turns without flipping during the solve. It became widely known through Tommy Cherry; the original proposer is uncertain. Memorisation and pin-order choices belong together: amounts from one execution order must not be used with another. This is not the front-then-back flip method, and generic wheel-turn solutions are not 7-simul algorithms.

The flip variant uses simultaneous turns with a flip, reducing the memorisation burden compared with the no-flip approach. Learn a complete consistent pin order from a specialist tutorial before changing individual fingertricks; do not combine the inspection rules of one variant with another's execution.