A chop move is a category of move, some of which are conventions and some of which are techniques.
The idea is that, when one of those moves happen, a player will "move his chop" (hence the name "Chop Move") by one slot. The card that previously was the chop is now considered as if it had been touched by a good-touch clue, and will be useful later. The card is not actually clued, but is treated as if it was, and no longer taken into account when figuring out which card is the oldest unclued card (chop).
Cards that are chop moved are considered good-touched, therefore useful later, but since there is no information on them (you know neither the color nor the number, just that it's useful), they are not considered when evaluating prompts. It is, sometimes, possible to figure out what the chop moved card was from the type of chop move that saved it and the remaining useful cards. For example, since the team doesn't care about saving 4s early in the game (not to be confused with "in the early game") at a point where no 4 was critical, if you get chop moved early on, you can assume it's a useful card that is not a 4.
When calculating the focus of a subsequent clue, chop moved card are treated like clued cards, so they aren't the focus unless there is no newly clued card involved, they will only be a collateral, but sometimes a collateral information is enough to play it, like any other non-focused card.
Chop moves are not immediately visible from the bare rules of the game (ex: if you ask someone "what do you know", they aren't allowed to mention chop moves, only actual clues), because the card isn't officially clued, so you have to rely on people paying attention to make sure everyone knows the chop move happened. Trust your team mates.
Obviously, the chop move only affects the specific card, not the slot, so when this card is gone, the chop goes back to it's normal slot.
- If you receive "5" on a card exactly one slot away from chop, it is a save clue on both the 5 and the current chop.
- If someone clues one or many cards that are obviously trash (and not on chop) and not a single useful card in a clue, they want you to discard those before your other cards. Chop move every card older than the oldest trash that got touched
- If the player on your left is about to discard a critical card and you can't save it, but he expects you to play something, discard instead to let him know he needs to use a clue right now.
- If a tempo clue happens for no obvious purpose, and you would have had nothing to do other than discarding on this turn, it should be taken as a chop move.