The OWL cut will remove events where there is a large amount of activity in the outer tubes. There are two principle ways that this is done. The first is to look for an above threshold number of OWLs and/or BUTTs. The second is to look for OWL triggers.
The parameters controling this cut are in FTLH 14
*DO FLTH 14 -i(35I -F) #. FLTH: Owl Cut #. 19750101 0 20380517 03331900 6*0 #. Standard Database Header 19750101 0 20380517 03331900 16*0 1 #.Cut mode =0 Owls or Butts, =1 Owls + Butts 5 #.Owl threshold cut if this or more. 2 #.Butt threshold cut if this or more. 5 #.Owl + butt threshold cut if this or more. 1 #.Cut OWL triggers =0 no, =1 yes 10*0.