This tool is designed to re-round and re-size the open hole (French) chimney in flutes. Enlarging the chimney can be a helpful remedy when the open hole pad retainer (a.k.a. bushing or grommet) is loose at the depth of desirable insertion.
This is particularly important when deeper insertion over-compresses and distorts the pad.
Directions: With the pad removed from the key cup, insert the small end of the tool into the chimney with a slight twisting movement and slight pressure into the chimney. This will slightly expand the chimney to allow the grommet to catch. Use only slight pressure please. It is better to work on the chimney more than once rather than to over tighten the fit. The slight chimney expansion will not affect the playing of the flute.