Apostrophe Lens
Flip the tile, then drag the lens across the gap and READ what comes out. Lock it in only once the sentence you can see actually works.
Both spellings sound identical, so your ear is no help and your eye has to do the work. There is one test and it never fails: STRETCH IT OUT. your / you're, whose / who's, their / they're, its / it's - the one with the apostrophe is two words squashed together, and the apostrophe marks the letters that went missing. Put the long version back into the sentence and read it: "the fox slipped into it is burrow" collapses immediately, so that gap wants the plain spelling. The plain spelling is a determiner, which means it has to own the next thing along - a coat, a name, a burrow. Watch out for the ones where a describing word gets in the way: "its enormous shadow" still owns the shadow, so the word straight after the gap is not always the test. That is also why "whose" and "who's" trip people up: "whose" owns something, "who's" is "who is". Run the stretch test out loud every single time and this stops being a guess.
What to say if they get stuck
- The lens does the test for you. Stretch the word out: if the long version reads properly, the apostrophe belongs there.
- An apostrophe is not a signpost for ownership. It is standing in for letters that have been taken out, which is why the lens can unpack it.
- Look at the word straight after the gap. If it is a thing somebody could own, you need the plain spelling. If it is a doing word or a describing word, nothing can own it, and you need the stretched-out one.