E/F Sharp Trill Key
The touch is placed between the first and second finger keys of the left hand, similar to the E/F sharp trill key of the bassoon. 

E/F Sharp Trill Key

E/F Sharp Trill Key with Special Right Forefinger E Flat Key
Normally, the Alternate E Flat Key for Right Forefinger conflicts with the E/F sharp trill and must be deleted.  This special arrangement of the forefinger E flat allows them to coexist.