I read them on the scale book of flute *ABRSM, on the page where flute key-work is labeled.

I have never used them, not even when i played the trills. Can somebody tell me where these keys are for.

I've used the trill keys when trilling from C or C# to D...

Yes, they're used if you need to trill between registers (any combination of C and C#/Db trilling to D or D#/Eb). They are also used for top Bb and top B: top Bb is fingered LH thumb, RH 1 and 1TR; top B is LH thumb, 1, 3 and RH 2TR.

I can't believe I forgot about top Bb and B. I've used them for that too

Think of it as a good thing, you obviously play those Bs so naturally, you don't even think about where your fingers need to be.

thks , is there a trill fingering chart anywhere that I can read?

woodwind.org they have trill fingerings and every combination of fingerings possible including the dreaded tremalos.

Click here to get started with flute fingering charts : I think these are invaluable.

Wow: I knew in theory that D in the 4th octave was possible (Prokofiev), but not that there was a whole 4th octave! . . . and so many alternative fingerings: It reminds me of guitar chord charts, where they often give at least 6 ways to play any given chord and the trick is to find the shape that fits best with the flow.

There are pieces that go up to 4th octave F - can't think what at the moment though.