Nobetan (literally "stretched single") is a tenpai wait shape made of four tiles in sequence, such as 4567m. It reads two ways: 456 as a complete run plus a 7 waiting to pair, or 567 as a complete run plus a 4 waiting to pair. The hand therefore completes on either the 4 or the 7, and whichever tile arrives becomes the pair.
Because the winning tile always forms the pair, nobetan is a tanki wait at heart, spread across two tile kinds. This gives it up to six unseen copies of ukeire, three at each end. Both ends count for furiten: if either 4 or 7 sits in your kawa, or you passed either one after riichi, ron is blocked across the entire wait.
For scoring, nobetan remains a tanki wait: it earns 2 fu and blocks pinfu, which requires a ryanmen wait. Compared with a tanki on one tile type, it offers more theoretical copies at equal shanten; yaku, dora, visible copies and safety can still change the choice.