As a reed begins to wear out a, trimmer can often restore some of its strength. It can also be used for reeds that feel just a little soft from new. Because it shortens the reed, the cane will become proportionately thicker at the tip and therefore feel harder again. This can prolong the life of the reed or repair a slightly damaged tip. However, because the reed loses it ability to vibrate as it is shortened, this procedure can only be used successfully once or twice.
There are two types on the market: the legendary Cordier (good ones that dont shred the tip can be hard to find) and those with a flexibe, adjustable knife which cut cleanly.