Usually after “short” vowels in words with more than one syllable.
inn |
Anna annex annoy annul banner bonnet bunny canning cannon cannot channel connect connive connote cranny dinner Donna dunnart fennel Finnish funnel funny gannet granny grinning henna innate inner innings kennel manna manner minnow penny pinna planner punnet rennet runner running runny scanner sinner skinny sonnet spanner spinner spinning stunner sunny tanner tanning tennis thinner thinning tinny tunnel uncanny unpinned winner winning |
This a really good website for teaching!