The F Attachment, also referred to as the Trigger or just Valve, is an additional length of tubing opened by a rotary valve that lowers the instrument a perfect 4th into the key of F.  This allows for additional alternate positions (low C in 1st, low B natural in lowered 2nd) as well as extending the low range from low E to the pedal Bb.  One important caveat is the the F attachment positions are not the same as the standard positions, they are lower and spaced further apart.

​On this page are links to:
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- My Video on this topic

Below that is a link that will open up a PDF in a new window, to save or print:

- An F Attachment Position Chart that shows where the F positions are on the slide in relation to the standard positions, and all the new notes available with the F valve.