O

O – open pass – The vessel traverses the lock with no lock hardware operation/chambering. The vessel goes straight through the chamber with both sets of gates open. This may occur at tidal locks.

F

F - fast double (Multi-chamber) – The towboat and possibly some of its barges are separated from the remaining barges and are locked through a different chamber from the remaining barges.

J

J - jack knife – The tow is rearranged, usually from two barges wide to three, by breaking the face coupling on at least one barge and knockout of the tow (and the towboat is moved alongside the barges).

K

K – knockout – The towboat alone is separated from its barges and moved alongside the barges for lockage.

N

N - navigable pass – The vessel traverses the dam instead of the lock. The vessel actually navigates outside the lock walls.

S

S – straight – The tow and/or its barges are not broken up for lockage.

T

T - barge transfer – Barges are placed in the lock chamber by one towboat, removed and continued on their journey with another towboat.

V

V – setover – The towboat and one or more of its barges are separated as a unit from the remaining barges to be “set over” for service. Tow and barges are moved alongside the barges for lockage.

Z

Z - other (remarks) – Any type of lockage not defined by one of the above.